ACC: How to Dial a Phone Number Using MS Access 95/97

• Microsoft Access versions 7.0, 97

SUMMARY

Advanced: Requires expert coding, interoperability, and multiuser skills.

This article describes a sample user-defined Visual Basic for Applications procedure, DialNumber(), that you can use to dial a telephone number from Microsoft Access using your computer's modem. This method uses Microsoft Windows application programming interface (API) procedure calls.

NOTE: Although this procedure works in Microsoft Access 7.0 and 97, those versions have an AutoDialer feature that you can use for dialing telephone numbers. Note, however, that the AutoDialer feature may not work on all Windows NT systems because it uses telephony application programming interface (TAPI) procedures to dial a phone, and TAPI is not included with Windows NT 3.51. This article does not use TAPI; therefore, the procedure in this article works on all Win32 systems.

For more information about the AutoDialer feature of Microsoft Access 7.0 and 97, search the Help Index for "AutoDialer."

For more information about using TAPI in Windows 95 and Windows NT 4.0, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q141625
   TITLE:      ACC: Using TAPI to Dial a Phone Under Win95/NT 4.0 (95/97)

MORE INFORMATION

Communications under Win32 have been simplified to use standard Windows file functions, such as CreateFile(), WriteFile(), and CloseHandle().

The following steps demonstrate how to create and use the DialNumber() function in Microsoft Access.

1. Open the sample database Northwind.mdb.

2. Create a module and type the following line in the Declarations section:

   NOTE: You may have some Microsoft Windows API functions defined in an existing Microsoft Access library; therefore, your declarations may be duplicates. If you receive a duplicate procedure name error message, remove or comment out the declarations statement in your code.

   NOTE: All Declare statements must be typed exactly as shown, including capitalization, because Win32 names are case-sensitive. To help eliminate errors by you or others who use your Declare statements, create Alias clauses for Declare statements that do not have an existing Alias. As long as the Alias is correctly spelled and capitalized, it doesn't matter how the function name is capitalized.

         Option Explicit
         Declare Function WriteFile& Lib "kernel32" _
            (ByVal hFile As Long, lpBuffer As Any, _
            ByVal nNumberOfBytesToWrite&, _
            lpNumberOfBytesWritten&, ByVal lpOverlapped&)
         Declare Function CreateFile& Lib "kernel32" Alias "CreateFileA" _
            (ByVal lpFileName$, ByVal dwDesiredAccess&, _
            ByVal dwShareMode&, ByVal lpSecurityAttributes&, _
            ByVal dwCreationDisposition&, ByVal dwFlagsAndAttributes&, _
            ByVal hTemplateFile&)
         Declare Function CloseHandle& Lib "kernel32" (ByVal hObject&)
         Declare Function FlushFileBuffers& Lib "kernel32" (ByVal hFile&)
   
         ' The number of seconds to wait for the modem to dial before
         ' .. resetting the modem. If the phone hangs up prematurely
         ' .. try increasing this value by small increments.
         Public Const WAITSECONDS = 4
   
         Public Const ID_CANCEL = 2
         Public Const MB_OKCANCEL = 1
         Public Const MB_ICONSTOP = 16, MB_ICONINFORMATION = 64
   
   

3. Type the following procedure:

         Function DialNumber(PhoneNumber, CommPort As String)
         ' PURPOSE: To dial a telephone number using the computer's modem
         ' ARGUMENTS:
         '    PhoneNumber: The telephone number to dial
         '    CommPort: The communications port the modem is connected
         '              to. Typically, modems are found on COM2, however,
         '              they can be configured for any COM port.
         '
         ' EXAMPLE:
         '    Type the following in the Immediate window using a modem
         '    connected to the COM2 port:
         '
         '       ? DialNumber("555-1212", "COM2")
         '
         ' ***********************************************************
   
            Dim Msg As String, MsgBoxType As Integer, MsgBoxTitle As String
            Dim bModemCommand(256) As Byte, ModemCommand As String
            Dim OpenPort As Long
            Dim RetVal As Long, RetBytes as Long, i as integer
            Dim StartTime
   
            ' Ask the user to pick up the phone.
            Msg = "Please pickup the phone and choose OK to dial " _
               & PhoneNumber
            MsgBoxType = MB_ICONINFORMATION + MB_OKCANCEL
            MsgBoxTitle = "Dial Number"
            If MsgBox(Msg, MsgBoxType, MsgBoxTitle) = ID_CANCEL Then
               Exit Function
            End If
   
            ' Open the communications port for read/write (&HC0000000).
            ' Must specify existing file (3).
            OpenPort = CreateFile(CommPort, &HC0000000, 0, 0, 3, 0, 0)
            If OpenPort = -1 Then
               Msg = "Unable to open communication port " & CommPort
               GoTo Err_DialNumber
            End If
   
            ' Send the telephone number to the modem.
            ModemCommand = "ATDT" & PhoneNumber & vbCrLf
            ' Pack the string in a Byte array.
            For i = 0 To Len(ModemCommand) - 1
               bModemCommand(i) = Asc(Mid(ModemCommand, i + 1, 1))
            Next
   
            ' Write the string to the Com port.
            RetVal = WriteFile(OpenPort, bModemCommand(0), _
               Len(ModemCommand), RetBytes, 0)
            If RetVal = 0 Then
               Msg = "Unable to dial number " & PhoneNumber
               GoTo Err_DialNumber
            End If
   
            ' Flush the buffer to make sure it actually wrote
            RetVal = FlushFileBuffers(OpenPort)
   
            ' Wait WAITSECONDS seconds for the phone to dial.
            StartTime = Timer
            While Timer < StartTime + WAITSECONDS
               DoEvents
            Wend
   
            ' Reset the modem and take it off line.
            ModemCommand = "ATH0" & vbCrLf
            ' Pack the byte array again.
            For i = 0 To Len(ModemCommand) - 1
               bModemCommand (i) = Asc(Mid(ModemCommand, i + 1, 1))
            Next
            RetVal = WriteFile(OpenPort, bModemCommand(0), _
               Len(ModemCommand), RetBytes, 0)
   
            'Flush the buffer again.
            RetVal = FlushFileBuffers(OpenPort)
   
            ' Close the communications port.
            RetVal = CloseHandle(OpenPort)
   
            Exit Function
   
         Err_DialNumber:      'This is not an On Error routine.
            Msg = Msg & vbCr & vbCr & _
               "Make sure no other devices are using Com port " & CommPort
            MsgBoxType = MB_ICONSTOP
            MsgBoxTitle = "Dial Number Error"
            MsgBox Msg, MsgBoxType, MsgBoxTitle
   
         End Function
   
   

4. Open the Employees form in Design view.

5. Add a command button next to the Home Phone field and set the following properties:

         Command Button:
            Name: btnDialPhone
            Caption: Dial
            OnClick: =DialNumber([HomePhone], "COM2")
   
   

6. View the form in Form view. To dial an employee's home phone number, click the Dial button.

REFERENCES

For information about how to dial a phone number in Microsoft Access 1.x and 2.0, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q93696
   TITLE     : ACC: How to Dial a Phone Number in Microsoft Access
               (1.x/2.0)