代码这样写最间单了：
Private Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
Select Case Shift
Case 1
MsgBox "你按下了shift"
Case 2
MsgBox "你按下了ctrl"
Case 4
MsgBox "你按下了alt"
Case 3
MsgBox "你按下了shift+ctrl"
Case 7
MsgBox "你按下了shift+ctrl+alt"
Case 5
MsgBox "你按下了shift+alt"
Case 6
MsgBox "你按下了ctrl+alt"
End Select
End Sub