主题：组合框出错

If e.DataCol.name ="商户注册手机号掩码" Then
    If e.NewValue = "" Then
        systemready = False
        e.DataRow(e.DataCol.name.SubString(0,e.DataCol.name.length-4)) = ""
        systemready = True
    ElseIf e.newvalue.contains("*") = False  Then
        Dim r_tele As New System.Text.RegularExpressions.Regex("^1[0-9]{10}$")
        If r_tele.IsMatch(e.newvalue) = False Then
            msgbox("电话号码不正确")
            e.cancel = True
           End If
        If e.Cancel = False Then
            systemready = False
            e.DataRow(e.DataCol.name.SubString(0,e.DataCol.name.length-2)) = e.newvalue
            e.NewValue = e.NewValue.SubString(0, 3) & "*****" & e.NewValue.SubString(8,3)
            systemready = True
        End If
    Else
        msgbox("不能这样修改")
        e.cancel = True
    End If
End If

如果在文本框中输入是手机号后单击保存不出错，如果是组合框选择带掩码的数据后就会出错,弹出“不能这样修改”提示，怎么处理？