Passing strings between different apps **RESOLVED**

[amitabh]

How do I send a string as a message between two apps using SendMessage or PostMessage?
This is the code I have, but it doesn't work, since I think I will have to use WM_COPYDATA with SendMessage, as suggested by MerrionComputin.
'In the first project

'in a form with a command button
Private Sub Form_Load()
    Me.Caption = "Test Target Window"
    Command1.Caption = "Test_Target_Button"
    'subclass the command button
    lngPrevWndProc = SetWindowLong(Command1.hWnd, GWL_WNDPROC, AddressOf WindowProc)
End Sub
 
Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
    'set it back to normal before exiting
    SetWindowLong Command1.hWnd, GWL_WNDPROC, lngPrevWndProc
End Sub
 
'=====================
'in a module
Public Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
 
Public Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hWnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
 
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal Length As Long)
'\\ Pointer validation in StringFromPointer
Private Declare Function IsBadStringPtrByLong Lib "kernel32" Alias "IsBadStringPtrA" (ByVal lpsz As Long, ByVal ucchMax As Long) As Long
 
 
Public Const GWL_WNDPROC = (-4)
 
Public lngPrevWndProc As Long
Public Const WM_USER = &H400
Public Const MY_MSG = WM_USER + 100
 
Public Function WindowProc(ByVal hWnd As Long, ByVal uMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
    Select Case uMsg
        Case MY_MSG
            MsgBox StringFromPointer(lParam, 12)
            'what to do here
            'lParam returns a pointer, how do I get the string
        Case Else
            WindowProc = CallWindowProc(lngPrevWndProc, hWnd, uMsg, wParam, lParam)
    End Select
End Function
 
Public Function StringFromPointer(lpString As Long, lMaxLength As Long) As String
 
  Dim sRet As String
  Dim lret As Long
 
  If lpString = 0 Then
    StringFromPointer = ""
    Exit Function
  End If
 
  If IsBadStringPtrByLong(lpString, lMaxLength) Then
    '\\ An error has occured - do not attempt to use this pointer
      StringFromPointer = ""
    Exit Function
  End If
 
  '\\ Pre-initialise the return string...
  sRet = Space$(lMaxLength)
  CopyMemory ByVal sRet, ByVal lpString, ByVal Len(sRet)
  If Err.LastDllError = 0 Then
    If InStr(sRet, Chr$(0)) > 0 Then sRet = Left$(sRet, InStr(sRet, Chr$(0)) - 1)
  End If
 
 
  StringFromPointer = sRet
 
End Function

In the second project:

'in a form with a command button
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
(ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Integer, ByVal lParam As String) As Long
 
Private Declare Function PostMessage Lib "user32" Alias "PostMessageA" (ByVal hwnd As Long, _
ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
 
Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" _
(ByVal hWnd1 As Long, ByVal hWnd2 As Long, ByVal lpsz1 As String, ByVal lpsz2 As String) As Long
 
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" _
(ByVal lpClassName As String, ByVal lpWindowName As String) As Long
 
Private Const WM_USER = &H400
Private Const MY_MSG = WM_USER + 100
 
Private Sub Command1_Click()
Dim lngFrmHwnd As Long
Dim lngBtnHwnd As Long
    lngFrmHwnd = FindWindow(vbNullString, "Test Target Window")
    lngBtnHwnd = FindWindowEx(lngFrmHwnd, 0&, vbNullString, "Test_Target_Button")
    SendMessage lngBtnHwnd, MY_MSG, 0&, "hello world"
    
End Sub

I am also attaching the code.

Thanks
Amitabh Kant