If e.DataCol.Name = "订货日期" Then
    If e.DataRow.IsNull("订货日期") Then
        e.DataRow("订单编号") = Nothing
    Else
        Dim d As Date = e.DataRow("订货日期")
        Dim y As Integer = d.Year
        Dim m As Integer = d.Month
        Dim Days As Integer = Date.DaysInMonth(y,m,d)
        Dim fd As Date = New Date(y,m,1)
        Dim ld As Date = New Date(y,m,Days) 
        Dim bh As String = Format(d,"yyyyMMdd") 
        If e.DataRow("订单编号").StartsWith(bh) = False
            Dim max As String
            Dim idx As Integer

            e.DataRow("订单编号")  = Nothing
            max = e.DataTable.Compute("Max(订单编号)","订货日期 >= #" & fd & "# And 订货日期 <= #" & ld & "#") 

            If max > "" Then 

                idx = CInt(max.Substring(7,3)) + 1 

            Else
                idx = 1 

            End If
            e.DataRow("订单编号") = bh & "-" & Format(idx,"000")
        End If
    End If
End If