ACC: "Syntax Error in String" Error Using DDE() and DDESend()

• Microsoft Access versions 2.0, 7.0

SYMPTOMS

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

When you enter either the DDE() or the DDESend() function in the ControlSource property of a text box on a form, you may receive the following error message:

   In Microsoft Access for Windows 95 version 7.0:

      The expression you entered has an invalid string

   In Microsoft Access version 2.0:

      Syntax error in string

NOTE: Visual Basic for Applications (used in Microsoft Access for Windows 95 version 7.0) is called Access Basic in version 2.0. For more information about Access Basic, please refer to the "Building Applications" manual.

CAUSE

A reference to another control is being used for the application or topic argument in the function. Note that you can successfully include a control reference for the item or data argument.

RESOLUTION

The following example demonstrates how to create and use the sample Visual Basic for Applications or Access Basic functions newDDE() and newDDESend() in place of the DDE() and DDESend() functions:

1. Open a module and enter the following code:

         Option Explicit
   

         Function newDDE (App, Topic, Item)
   

            Dim chan
            On Error GoTo ErrnewDDE
            chan = DDEInitiate(App, Topic)
            newDDE = DDERequest(chan, Item)
            DDETerminate chan
   
         ByenewDDE:
            Exit Function
   
         ErrnewDDE:
            newDDE = "#DDEERROR"
            Resume ByenewDDE
   
         End Function
   
         Function newDDESend (App, Topic, Item, DataToSend)
            Dim chan
            On Error GoTo ErrnewDDESend
            chan = DDEInitiate(App, Topic)
            DDEPoke chan, Item, DataToSend
            DDETerminate chan
            newDDESend = True
   
         ByenewDDESend:
            Exit Function
   
         ErrnewDDESend:
            newDDESend = False
            Resume ByenewDDESend
   
         End Function
   
   

2. Start Microsoft Word for Windows, version 7.0. Save a new document as Test.

3. Type a few lines of text in the document, and then select the text.

4. Click Bookmark on the Edit menu. Type "MyBookMark" (without the quotation marks), and then press ENTER.

5. Switch to Microsoft Access (leave Word for Windows running).

6. Create a new form with the following controls and properties:

         Text box:
           Name: App
         Text box:
           Name: Topic
         Text box:
           Name: Item
         Text box:
           Name: Data
         Text box:
           Name: DDE
           ControlSource: =newDDE([App],[Topic],[Item])
         Text box:
           Name: DDESend
           ControlSource:
              =newDDESend([App],[Topic],[Item],[Data])
           Format: True/False
   
   

7. On the View menu, click Form. Note that "#DDEError" appears in the DDE text box, and "False" appears in the DDESend text box. These messages occur because there are not yet valid application, topic, and item arguments.

8. Create the following entries:

         App: Winword
         Topic: Test
         Item: MyBookMark
         Data: Hello!
   

   Note that the DDESend box displays "True," and the text "Hello!" appears in the Word for Windows document.

9. With the insertion point in the DDE box, press F9 to force the function to refresh. Note that "Hello!" appears in the DDE box in place of "#DDEError."

STATUS

This behavior is by design.

MORE INFORMATION

When the form is opened, Microsoft Access immediately establishes a DDE channel to the other application. This link uses the application and topic arguments in the function. The channel is kept open until the form is closed. Because the channel is open, the arguments necessary for opening the channel cannot be altered.

Microsoft Access does not open a new channel whenever it needs to call or refresh the control with the DDE() or DDESend() function. Doing so would impose significant overhead and could result in performance degradation.

Steps to Reproduce Behavior

1. Create a blank, unbound form.

2. Add a text box to the form.

3. Enter any of the following expressions in the text box's ControlSource property:

         =DDE("winword",[topic],"my item")
   

         =DDE([app],"MyDoc","my item")
   

         =DDESend("winword",[topic],"my item, "my data")
   

         =DDESend([app],"MyDoc","my item, "my data")
   

REFERENCES

For more information about sharing data between applications, search for "dynamic data exchange (DDE)," and then "Overview" using the Microsoft Access for Windows 95 Help Index.

Microsoft Access "User's Guide", version 2.0, pages 735, 740

Microsoft Access "Building Applications", version 2.0, pages 295-298

Keywords          : IntpDde
Version           : 2.0 7.0
Platform          : WINDOWS
Hardware          : x86
Issue type        : kbdocerr