主题：[求助]执行次数

老师，如果 5次输入错误 就退出系统，代码该如何修改？

Dim txt As String = e.Form.Controls("TextBox1").Text
Dim tbl As DataTable = DataTables("激活码")
If txt = "" Then
    tbl.LoadFilter = ""
Else
    txt = "'%" & txt & "%'"
    tbl.LoadFilter = "激活码 Like " & txt
    tbl.Load()
   
    If tbl.DataRows.Count = 0 Then
        MessageBox.Show("您输入的激活码不正确,请重新输入!","提示",MessageBoxButtons.OK,MessageBoxIcon.Warning)
    End If
End If