按窗体右上角关闭按钮后,如不满足一定条件则取消关闭操作怎么实现

按窗体右上角关闭按钮后,如不满足一定条件则取消关闭操作如何实现
我做了程序,为了避免出现错误,当按窗体右上角关闭按钮后,如果程序正在执行某个操作,则取消关闭操作!~这个能否实现,请各位帮帮忙

[解决办法]
Private Sub Form_Unload(Cancel As Integer)
If MsgBox( "确退出? ", vbYesNo + vbInformation, "提示 ") = vbNo Then
Cancel = True
Exit Sub
End If
End Sub
[解决办法]
Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
If MsgBox( "是否关闭 ", vbYesNo) = vbNo Then
Cancel = 1
End If
End Sub

[解决办法]
Private Sub Form_Unload(Cancel As Integer)
If MsgBox( "确认退出? ", vbDefaultButton2 + vbOKCancel) = vbCancel Then Cancel = 1
把Msgbox语句换成条件就可
End Sub