Option Explicit
 
Private Declare Function GetAsyncKeyState Lib "user32" _
        (ByVal vKey As Long) As Integer
 
Private Sub Timer1_Timer()
 
  If GetAsyncKeyState(vbLeftButton) = -32767 Then
    Debug.Print "Linke Maustaste gedrückt"
  End If
 
  If GetAsyncKeyState(vbRightButton) = -32767 Then
    Debug.Print "Rechte Maustaste gedrückt"
  End If
End Sub