主题：[求助]datacolchanged判断语句出错

代码为：

Dim lower As Single = Tables("检验明细").Current("Min")
Dim uper As Single = Tables("检验明细").Current("Max")
Dim m As Single = Tables("检验明细").Current("测量值")
Dim b As Boolean
If e.DataCol.Name = "测量值" AndAlso m <> Nothing Then
    If lower <> Nothing Then
        If uper <> Nothing
            b = (m >= lower) And (m <= uper)
        Else
            b = (m >= lower)
        End If
    Else
        If uper <> Nothing Then
            b = (m <= uper)
        End If
    End If
Else
    Tables("检验明细").Current("判别") = ""
End If
If b = True Then
    Tables("检验明细").Current("判别") = "OK"
Else
    Tables("检验明细").Current("判别") = "NG"
End If

在表中执行时出错，求教问题在哪儿？