主题：流水账的制作

我想做通用的流水账，格式为数量金额式的，余额方向有借方、贷方两种情况，修改标颜色以上的代码，希望当余额方向不同时按不同计算方向，执行时提示错误，该怎么修改？帮助中只考虑了“产品”一个因素，实际中可能有两个以上的因素，标颜色以下的e.OldValue、e.newvalue，该怎么改

Select Case e.DataCol.Name
    Case "会计科目","借方_数量","贷方_数量"，"项目"，“方向”
        Dim dr As DataRow
        Dim mr As DataRow = e.DataRow
        Dim drs As List(of DataRow)
        dr = e.DataTable.Find("[_SortKey] < " & mr("_SortKey") & " And [会计科目] = '" & mr("会计科目") & "'And [项目] = '" & mr("项目") & "'", "[_SortKey] Desc")
        If dr Is Nothing Then
            If dr("方向") = "借方" Then
                mr("余额_数量") = mr("借方_数量") - mr("贷方_数量")
                mr("余额_金额") = mr("借方_金额") - mr("贷方_金额")
                dr = mr
            Else
                mr("余额_数量") = mr("贷方_数量") - mr("借方_数量")
                mr("余额_金额") = mr("贷方_金额") - mr("借方_金额")
                dr = mr
            End If
        End If
        drs = e.DataTable.Select("[_SortKey] >= " & dr("_SortKey") & " And [会计科目] = '" & dr("会计科目") & "'And [项目] = '" & mr("项目") & "'", "[_SortKey]")
        For i As Integer = 1 To drs.Count - 1
            If drs(i)("方向") = "借方" Then
                drs(i)("余额_数量") = drs(i-1)("余额_数量") + drs(i)("借方_数量") - drs(i)("贷方_数量")
                drs(i)("余额_金额") = drs(i-1)("余额_金额") + drs(i)("借方_金额") - drs(i)("贷方_金额")
            Else
                drs(i)("余额_数量") = drs(i-1)("余额_数量") - drs(i)("借方_数量") + drs(i)("贷方_数量")
                drs(i)("余额_金额") = drs(i-1)("余额_金额") - drs(i)("借方_金额") + drs(i)("贷方_金额")
            End If
        Next

                           
        If e.DataCol.Name = "会计科目" AndAlso e.OldValue IsNot Nothing AndAlso e.OldValue <> e.NewValue Then
            dr = e.DataTable.Find("[_SortKey] < " & mr("_SortKey") & " And [会计科目] = '" & e.OldValue & "'", "[_SortKey] Desc")
            If dr Is Nothing Then
                dr = e.DataTable.Find("[会计科目] = '" & e.OldValue & "'", "[_SortKey]")
                If dr IsNot Nothing Then
                    dr("余额_数量") = dr("借方_数量") - dr("贷方_数量")
                    dr("余额_金额") = dr("借方_金额") - dr("贷方_金额")
                End If
            End If
            If dr IsNot Nothing Then
                drs = e.DataTable.Select("[_SortKey] >= " & dr("_SortKey") & " And [会计科目] = '" & dr("会计科目") & "'And [项目] = '" & mr("项目") & "'", "[_SortKey]")
                For i As Integer = 1 To drs.Count - 1
                    drs(i)("余额_数量") = drs(i-1)("余额_数量") + drs(i)("借方_数量") - drs(i)("贷方_数量")
                    drs(i)("余额_金额") = drs(i-1)("余额_金额") + drs(i)("借方_金额") - drs(i)("贷方_金额")
                Next
            End If
        End If
End Select