PRB: SendKeys May Return Illegal Function Call Error

• Standard and Professional Editions of Microsoft Visual Basic for Windows, versions 2.0 and 3.0
• Microsoft Visual Basic programming system for Windows, version 1.0

SUMMARY

SYMPTOMS

   The SendKeys statement reports the error "Illegal function call" when
   its argument contains an incorrectly formatted string. This article
   describes specific circumstances that cause this error, and contains
   a code example that shows how to send any string with SendKeys.

   The following characters have special meaning to the SendKeys statement:

      + ^ % ~ ( ) [ ] { }

   The SendKeys statement reports an "Illegal function call" error if its
   argument contains one of the following, not enclosed in braces:

    - An unmatched parenthesis () or bracket {}
    - A bracket []
    - Braces containing an undefined character sequence, such as {abc}

   To prevent the SendKeys statement from interpreting a character,
   enclose the character in braces {}. For example, to send the string

      The interest rate is 5% (annually).

   Use the following SendKeys syntax:

      SendKeys "The interest rate is 5{%} {(}annually{)}."

MORE INFORMATION

Step-by-Step Example

1. Start Visual Basic or from the File menu, choose New Project (ALT, F, N) if Visual Basic is already running. Form1 is created by default.

2. Place a text box (Text1) on Form1.

3. Place a command button (Command1) on Form1.

4. Enter the following code:

      Sub Command1_Click ()
         Text1.SetFocus
         SendKeys sendkeys_prepare("1+2^5% ")
         SendKeys sendkeys_prepare("[] ")
         SendKeys sendkeys_prepare("{abc}")
      End Sub
   
      ' The following function puts braces {} around characters that
      ' are special to the SendKeys statement.
      Function sendkeys_prepare (in As String) As String
         For i% = 1 To Len(in)
            ' Get the next character into c$.
            c$ = Mid$(in, i%, 1)
            ' If c$ is one of the special characters.
            If InStr("+^%~()[]{}", c$) Then
               out$ = out$ + "{" + c$ + "}"
            Else
               out$ = out$ + c$
            End If
         Next
         sendkeys_prepare = out$
      End Function
   
   

5. Press F5 to run the program. Click Command1. Some example text

   characters special to SendKeys appear in Text1.

REFERENCES

"Microsoft Visual Basic: Language Reference," version 1.0, pages 283-284