主题：流水账外部加载问题

各位老师你们好！帮我看看下面这段流水账的代码哪里有问题，非常感谢！

Select Case e.DataCol.Name
    Case "开户行","贷入","借出" 

        DataTables("银行借贷明细").Save
        Dim dr As DataRow
        Dim mr As DataRow = e.DataRow
        Dim drs As List(of DataRow)
        dr = e.DataTable.SQLFind("[_SortKey] < " & mr("_SortKey") & " And [开户行] = '" & mr("开户行") & "'", "[_SortKey] Desc")
        If dr Is Nothing Then
            mr("可支配余额") = mr("贷入") - mr("借出")
            dr = mr
        End If
        drs = e.DataTable.SQLSelect("[_SortKey] >= " & dr("_SortKey") & " And [开户行] = '" & dr("开户行") & "'", "[_SortKey]")
        For i As Integer = 1 To drs.Count - 1
            drs(i)("可支配余额") = drs(i-1)("可支配余额") + drs(i)("贷入") - drs(i)("借出")
        Next
        If e.DataCol.Name = "开户行" AndAlso e.OldValue IsNot Nothing AndAlso e.OldValue <> e.NewValue Then
            dr = e.DataTable.SQLFind("[_SortKey] < " & mr("_SortKey") & " And [开户行] = '" & e.OldValue & "'", "[_SortKey] Desc")
            If dr Is Nothing Then
                dr = e.DataTable.SQLFind("[开户行] = '" & e.OldValue & "'", "[_SortKey]")
                If dr IsNot Nothing Then
                    dr("可支配余额") = dr("贷入") - dr("借出")
                End If
            End If
            If dr IsNot Nothing Then
                drs = e.DataTable.SQLSelect("[_SortKey] >= " & dr("_SortKey") & " And [开户行] = '" & dr("开户行") & "'", "[_SortKey]")
                For i As Integer = 1 To drs.Count - 1
                    drs(i)("可支配余额") = drs(i-1)("可支配余额") + drs(i)("贷入") - drs(i)("借出")
                Next
            End If
        End If
End Select