Isn't the middle mouse button = 3?

Or you could just do it this way:

Code:
Private Sub Timer1_Timer()
If GetAsyncKeyState(vbLeftButton) Then Caption = "Left"
If GetAsyncKeyState(vbMiddleButton) Then Caption = "Middle"
If GetAsyncKeyState(vbRightButton) Then Caption = "Right"
End Sub
And did anyone ever see the new mouse with 4 buttons. Wonder how you detect that forth button. Or is that what 4 is equal to?