te paso una forma. ..Saludos
Código:
Declare Function GetAsyncKeyState Lib "user32" (ByVal vKey As Long) As Integer
Private Sub Form_Load()
Timer1.Interval = 50
End Sub
Private Sub Timer1_Timer()
If GetAsyncKeyState(1) = -32767 Then
Me.Caption = " Presionaste el Botón izquierdo "
End If
If GetAsyncKeyState(2) = -32767 Then
Me.Caption = " Presionaste el Botón derecho "
End If
End Sub