Private Declare Function SetWindowLong Lib "user32" Alias _
      "SetWindowLongA"  _
     (ByVal hwnd As Long, _
      ByVal nIndex As Long, _
      ByVal dwNewLong As Long) As Long
 
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 OldWndProg As Long
Private Const GWL_WNDPROC = (-4)
 
'Messages:
Private Const WM_MOUSEMOVE = &H200
 
'Diese Funktion "verbiegt - subclasst" Windows!
'Es wird dadurch möglich, dass statts der Standart Nachrichtenverarbeitung des
'Windows eine "eigene" Nachrichtenverarbeitung dazwischengehängt wird
 
Public Function ChangeWndProg(Byval hwnd As Long) As Long
       OldWndProg = SetWindowLong(hwnd,GWL_WNDPROC,AddressOf  WndProg)
End Function
 
Public Function ChangeOldWndProg(Byval hWnd As Long) As Long
      Dim RVal As Long
      RVal = SetWindowLong(hWnd, GWL_WNDPROC, OldWndProg)
End Function
 
 
'Das ist die "neue", unsere eigene Nachrichtenverarbeitung, die von Windows ab
'sofort aufgerufen wird. Es handelt sich um eine Windows-callback - Funktion
 
Public Function WndProg(Byval hwnd As Long, _
                                              Byval uMsg As Long, _
                                              Byval wParam As Long, _
                                              Byval lParam As Long) As Long
 
        'Bestimmte Nachrichten herauspicken, den Rest weiterleiten
        Select Case uMsg
                    Case WM_MOUSEMOVE
                            'hier z.B. wird die Mousbewegung eingefangen ...
                            Form1.Command1.Backcolor = vbred
        End Select
 
        WndProg = CallWindowProc(OldWndProg, hWnd, uMsg, wParam, Byval lParam)
End Function

Private Sub Command1_MouseMove(Button As Integer, Shift As Integer, X As _
  Single, Y As Single)
    Command1.BackColor = vbGreen
End Sub
 
Private Sub Form_Load()
   ChangeWndProg Me.hwnd
End Sub
 
Private Sub Form_Terminate()
   ChangeOldWndProg Me.hwnd
End Sub