Option Explicit
 
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" _
  (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
 
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
  (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, _
  lParam As Any) As Long
 
Dim DesthWnd As Long ' Holds the Process Handle
 
Const WM_USER As Long = &H400
 
Sub FindHandle()
        DesthWnd = FindWindow(vbNullString, "BISERV")
        If (DesthWnd = 0) Then
            Call MsgBox("Window not found!", vbOKOnly + vbExclamation)
            Exit Sub
        End If
    Call MsgBox("Handle: " & DesthWnd, vbOKOnly + vbExclamation)
End Sub
 
Private Sub Command1_Click()
    Call FindHandle
End Sub
 
 
Private Sub Command2_Click()
    Call SendText(Form1.Text1.Text)
End Sub
 
Private Sub SendText(t As String)
  Call SendMessage(DesthWnd, WM_USER + &H101, 25555, CLng(Asc(Mid(t, 1, 1))))
End Sub

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
  (ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, _
  lParam As Any) As Long
 
Option Explicit
 
Private Sub Form_Load()
    Call Init(Form1.hWnd)
End Sub
 
Private Sub Form_Unload(Cancel As Integer)
    Call Terminate(Me.hWnd)
End Sub

Private 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 Function SetWindowLong Lib "user32" Alias _
        "SetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As _
        Long, ByVal dwNewLong As Long) As Long
 
Const GWL_WNDPROC As Long = -4&
Const WM_COPYDATA As Long = &H4A
 
Dim PrevWndProc As Long
 
Public Sub Init(hWnd As Long)
    PrevWndProc = SetWindowLong(hWnd, GWL_WNDPROC, _
                              AddressOf WindowProc)
End Sub
 
Public Sub Terminate(hWnd As Long)
    Call SetWindowLong(hWnd, GWL_WNDPROC, PrevWndProc)
End Sub
 
Private Function WindowProc(ByVal hWnd As Long, ByVal Msg As Long, _
    ByVal wParam As Long, ByVal lParam As Long) As Long
 
    If Msg > WM_USER + &H100 Then
        Form1.Text1.Text = hWnd
        Form1.Text2.Text = Msg
        Form1.Text3.Text = wParam
        Form1.Text4.Text = lParam
    End If
 
    WindowProc = CallWindowProc(PrevWndProc, hWnd, Msg, wParam, lParam)
End Function