主题：[求助]多条件下的跨表引用问题

表B的DataColChanged事件设置以下代码

Dim dr As DataRow = e.DataRow
Select Case e.DataCol.Name
    Case "学年","年级","课程"
        If dr.IsNull(e.DataCol.Name) Then
            dr("学时") = Nothing
        Else
            Dim fdr As DataRow = DataTables("表A").find("学期='" & dr("学年") & "' and 年级='" & dr("年级") & "' and 课程='" & dr("课程") & "'")
            If fdr IsNot Nothing
                dr("学时") = fdr("学时")
            End If
        End If
End Select