Sending strings to other application (SendMessage API)

[hypermount]

I'm trying to create an application to send strings to other application's textbox.

Used these 2 functions but unable to sendmessage. It seems to manage to find the Window with the caption "Printing" but can't find the textbox.

Public Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Public 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
Public Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As String) As Long
Public Const EM_REPLACESEL = &HC2


'For Second method
'Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function SendMessageByString Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As String) 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 GetWindow Lib "user32" (ByVal hwnd As Long, ByVal wCmd As Long) As Long
Private Declare Function GetClassName Lib "user32" Alias "GetClassNameA" (ByVal hwnd As Long, ByVal lpClassName As String, ByVal nMaxCount As Long) As Long


Private Const WM_SETTEXT = &HC
Private Const GW_HWNDNEXT = 2
Private Const GW_CHILD = 5

Public Function barcode2(strBarcode As String)
Dim wnd As Long, meswnd As Long, lhndchild As Long
Dim StrClass As String * 255
Dim i As Integer

wnd = FindWindow(vbNullString, "Printing")

wnd = FindWindowEx(wnd, 0&, vbNullString, "Printing")

lhndchild = GetWindow(wnd, GW_CHILD)

'Continue enumuration
Do
    Call GetClassName(lhndchild, StrClass, 255)
    i = InStr(StrClass, "Edit")
    If i > 0 Then
       SendMessageByString lhndchild, WM_SETTEXT, 0, strBarcode
'       Me.CmdSend.Enabled = True
       Exit Function
    End If
    
    lhndchild = GetWindow(lhndchild, GW_HWNDNEXT)
    If lhndchild = 0 Then Exit Do

Loop

End Function

Public Sub barcode3(strBarcode As String)
    Dim hWndForm        As Long
    Dim hWndTextBox     As Long
    
    ' Find the destination window
    hWndForm = FindWindow(vbNullString, "Printing")
    
    If (hWndForm = 0) Then
        MsgBox "Couldn't find a destination window with that caption.", vbExclamation
        Exit Sub
    End If
    
    ' Find the text box as a child of the destination window
    hWndTextBox = FindWindowEx(hWndForm, 0&, "Edit", vbNullString)
    
    If (hWndTextBox = 0) Then
        MsgBox "Couldn't find target VB text box in the destination window.", vbExclamation
        Exit Sub
    End If
    
    ' If all's well, send the message.
    '
    ' Be aware that, in this example, until the message
    ' box is dismissed, this app will be hung.
    SendMessage hWndTextBox, WM_SETTEXT, 0&, ByVal CStr(strBarcode)
    
End Sub