VBA: Sample Code to Determine CD-ROM Drive Letter

ID: Q180766

The information in this article applies to:

• Microsoft Visual Basic for Applications version 5.0
• Microsoft Office 97 for Windows
• Microsoft Access 97
• Microsoft Excel 97 for Windows
• Microsoft PowerPoint 97 for Windows
• Microsoft Word 97 for Windows

SUMMARY

This article contains sample Microsoft Visual Basic for Applications code that determines the drive letter of the first CD-ROM drive and returns it to a variable as a string. It is then output to a message box. This would be useful for accessing files contained on a CD.

MORE INFORMATION

Microsoft provides programming examples for illustration only, without warranty either expressed or implied, including, but not limited to, the implied warranties of merchantability and/or fitness for a particular purpose. This article assumes that you are familiar with the programming language being demonstrated and the tools used to create and debug procedures. Microsoft support professionals can help explain the functionality of a particular procedure, but they will not modify these examples to provide added functionality or construct procedures to meet your specific needs. If you have limited programming experience, you may want to contact the Microsoft fee-based consulting line at (800) 936-5200. For more information about the support options available from Microsoft, please see the following page on the World Wide Web:

   http://www.microsoft.com/support/supportnet/refguide/

Sample Visual Basic Procedure

   ' **********************************************************************
   '
   ' FUNCTION:
   '    GetFirstCdRomDriveLetter()
   '
   ' PURPOSE:
   '    Finds the first CD-ROM device and then returns its drive letter.
   '
   ' ARGUMENTS:
   '    None
   '
   ' RETURNS:
   '    A string that represents the first CD-ROM drive letter. If the
   '    function fails for any reason, it returns vbNullString.
   '
   ' **********************************************************************
   Declare Function GetDriveType Lib "kernel32" Alias _
      "GetDriveTypeA" (ByVal nDrive As String) As Long

   Declare Function GetLogicalDriveStrings Lib "kernel32" Alias _
      "GetLogicalDriveStringsA" (ByVal nBufferLength As Long, _
      ByVal lpBuffer As String) As Long

   Public Const DRIVE_CDROM As Long = 5

   Function GetFirstCdRomDriveLetter() As String

      ' Declare variables.
      Dim lDriveType As Long
      Dim strDrive As String
      Dim lStart As Long: lStart = 1

      ' Create a string to hold the logical drives.
      Dim strDrives As String
      strDrives = Space(150)

      ' Get the logial drives on the system.
      ' If the function fails it returns zero.
      Dim lRetVal As Long
      lRetVal = GetLogicalDriveStrings(150, strDrives)

      ' Check to see if GetLogicalDriveStrings() worked.
      If lRetVal = 0 Then

         ' Get GetLogicalDriveStrings() failed.
         GetFirstCdRomDriveLetter = vbNullString
         Exit Function
      End If

      ' Get the string that represents the first drive.
      strDrive = Mid(strDrives, lStart, 3)

      Do

         ' Test the first drive.
         lDriveType = GetDriveType(strDrive)

         ' Check if the drive type is a CD-ROM.
         If lDriveType = DRIVE_CDROM Then

            ' Found the first CD-ROM drive on the system.
            GetFirstCdRomDriveLetter = strDrive
            Exit Function
         End If

         ' Increment lStart to next drive in the string.
         lStart = lStart + 4

         ' Get the string that represents the first drive.
         strDrive = Mid(strDrives, lStart, 3)

      Loop While (Mid(strDrives, lStart, 1) <> vbNullChar)

   End Function

   Sub Main

      Dim strDriveLetter as String

      ' Call the GetFirstCdRomDriveLetter() and store the
      ' return value in strDriveLetter.
      strDriveLetter = GetFirstCdRomDriveLetter()

      ' Display the drive letter in a message box.
      MsgBox strDriveLetter

   End Sub

REFERENCES

For more information about getting help with Visual Basic for Applications, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q163435
   TITLE     : VBA: Programming Resources for Visual Basic for
               Applications

Keywords          : OffVBA 
Version           : WINDOWS:5.0,97
Platform          : WINDOWS
Issue type        : kbhowto

Last Reviewed: April 6, 1999