主题：这个怎么回事?该怎么弄?

此主题相关图片如下：捕获3.png
,出现这种提示是哪里出问题了,请专家赐教!在表中增添_SortKey列又增加不上,该怎么做才能改好?我在表中DataColChanged中的代码是:

Select Case e.DataCol.Name
    Case "收入数","支出数"
        Dim dr As DataRow
        Dim drs As List(of DataRow)
        dr = e.DataTable.Find("[_SortKey] < " & e.DataRow("_SortKey"), "[_SortKey] Desc")
        If dr Is Nothing Then
            e.DataRow("收支结余累计数") = e.DataRow("收入数") - e.DataRow("支出数")
            dr1 = e.DataRow
        End If
        drs = e.DataTable.Select("[_SortKey] >= " & dr("_SortKey"), "[_SortKey]")
        For i As Integer = 1 To drs.Count - 1
            drs(i)("收支结余累计数") = drs(i-1)("收支结余累计数") + drs(i)("收入数") - drs(i)("支出数")
        Next   
End Select

谢谢