主题：有关error的问题

Dim n1 As Double = e.Form.Controls("NumericComboBox6").Text
Dim n2 As Double = e.Form.Controls("TextBox4").Text
If n1 <>  "" Then
    If n1 >= n2 Then
        e.Form.Controls("NumericComboBox6").Error = "取量要小于余量!"
    Else
        e.Form.Controls("NumericComboBox6").Error  = ""
    End If
End If

代码报错 怎么回事，帮忙看看哪写错啦！