主题：小组求和

Select Case e.DataCol.name
    Case "类别"
        If e.OldValue <> Nothing Then
            Dim sum As Double = e.DataTable.Compute("sum(数量)", "类别 = '" & e.oldvalue & "'")
            e.DataTable.replacefor("类别求和", sum, "类别 = '" & e.oldvalue & "'")
        End If
        If e.newValue <> Nothing Then
            Dim sum As Double = e.DataTable.Compute("sum(数量)", "类别 = '" & e.NewValue & "'")
            e.DataTable.replacefor("类别求和", sum, "类别 = '" & e.NewValue & "'")
        End If
    Case "数量"
        Dim sum As Double = e.DataTable.Compute("sum(数量)", "类别 = '" & e.datarow("类别") & "'")
        e.DataTable.replacefor("类别求和", sum, "类别 = '" & e.datarow("类别") & "'")
End Select