ACC: How to Use Dynamic Data Exchange (DDE) to Fill a List Box

ID: Q94003

The information in this article applies to:

• Microsoft Access versions 1.0, 1.1, 2.0, 7.0, 97

SUMMARY

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

This article shows you how to create a sample user-defined Visual Basic for Applications function that uses dynamic data exchange (DDE) to populate a list box.

This article assumes that you are familiar with Visual Basic for Applications and with creating Microsoft Access applications using the programming tools provided with Microsoft Access. For more information about Visual Basic for Applications, please refer to your version of the "Building Applications with Microsoft Access" manual.

NOTE: Visual Basic for Applications is called Access Basic in Microsoft Access versions 1.x and 2.0. For more information about Access Basic, please refer to the "Introduction to Programming" manual in Microsoft Access version 1.x or the "Building Applications" manual in Microsoft Access version 2.0

MORE INFORMATION

The following function uses DDE to retrieve a list of countries from Microsoft Excel. The list will be used to populate a list box bound to the Country field of the Suppliers table in the sample database Northwind.mdb (or NWIND.MDB in Microsoft Access versions 1.x and 2.0).

 1. In a new worksheet in Microsoft Excel, enter the following data in the
    first column:

       Cell   Value
       ----------------
       A1     Australia
       A2     China
       A3     Scotland

 2. Save the worksheet as COUNTRY.XLS.

 3. Open the sample database Northwind.mdb in Microsoft Access, and open a
    new module.

 4. Type the following lines in the Declarations section:

       Option Explicit
       Dim Countries(10) As String
       Dim CountryData As String

 5. Type the following Sub procedure:

      Sub DDEFillCountries ()
         Dim EndString%, i%
         Dim Chan

         EndString% = 0
         i% = 0
         Chan = DDEInitiate("Excel", "COUNTRY.XLS")
         CountryData$ = DDERequest(Chan, "R1C1:R10C1")
         DDETerminate Chan
         EndString% = InStr(1, CountryData, Chr(13))

         Do Until Len(CountryData$) = 0
            Countries(i%) = Left(CountryData, EndString% - 1)
            CountryData$ = Right(CountryData, _
                         Len(CountryData) - EndString% - 1)
            EndString% = InStr(1, CountryData, Chr(13))
            i% = i% + 1
         Loop

      End Sub

 6. Type the following function:

      Function DDEFillList (fld As Control, id, row, col, code)

         Select Case code
            Case 0
               Call DDEFillCountries
               DDEFillList = True
            Case 1
               DDEFillList = id
            Case 3
               DDEFillList = 10
            Case 4
               DDEFillList = 1
            Case 5
               DDEFillList = -1
            Case 6
               DDEFillList = Countries(row)
         End Select
      End Function

 7. Save the module as DDE Fill List Box.

 8. Create a new form based on the Suppliers table.

 9. Add a list box bound to the Country field and set the following
    property:

       RowSourceType: DDEFillList

    is open. Switch to Form view. Note that the list box is populated
    with the countries that you entered in Microsoft Excel.

• Error checking for the DDE portion to handle cases where Microsoft Excel is not running or is busy.
• Refreshing the form if needed to show updated data.

REFERENCES

For more information about filling a list box, search the Help Index for "list boxes," or ask the Microsoft Access 97 Office Assistant.

Additional query words:

Keywords          : kbprg kbusage FmsCmbo 
Version           : 1.0 1.1 2.0 7.0 97
Platform          : WINDOWS
Hardware          : x86
Issue type        : kbhowto

Last Reviewed: January 12, 1999