主题：三个条件筛选

Select Case e.DataCol.Name
    Case "产品","入库","出库"
        Dim dr As DataRow
        Dim mr As DataRow = e.DataRow
        Dim drs As List(of DataRow)
        dr = e.DataTable.Find("[_SortKey] < " & mr("_SortKey") & " And [产品] = '" & mr("产品") & "'", "[_SortKey] Desc")
        If dr Is Nothing Then '如果没有上一行,说明本行就是同产品的第一行
            mr("库存") = mr("入库") - mr("出库")
            dr = mr
        End If
        drs = e.DataTable.Select("[_SortKey] >= " & dr("_SortKey") & " And [产品] = '" & dr("产品") & "'")
        For i As Integer = 1 To drs.Count - 1 '重算余下行的余额
            drs(i)("库存") = drs(i-1)("库存") + drs(i)("入库") - drs(i)("出库")
        Next
End Select

这个代码在执行时为什么有错误提示

高手指导一下