主题：不load数据，自动编号重复问题

Select e.DataCol.Name
Case "制单日期","工程代码"
If e.DataRow.IsNull("制单日期") OrElse e.DataRow.IsNull("工程代码") Then
e.DataRow("单据编号") = Nothing
Else
Dim d As Date = e.DataRow("制单日期")
Dim y As Integer = d.Year
Dim m As Integer = d.Month
Dim Days As Integer = Date.DaysInMonth(y,m)
Dim fd As Date = New Date(y,m,1) '获得该月的第一天
Dim ld As Date = New Date(y,m,Days) '获得该月的最后一天
Dim bh As String = e.DataRow("工程代码") & "-" & Format(d,"yyyyMM") & "-" '生成编号的前缀
If e.DataRow("单据编号").StartsWith(bh) = False '如果单据编号前缀不符
Dim max As String
Dim idx As Integer
Dim flt As String
flt = "工程代码 = '"& e.DataRow("工程代码") & "' And 制单日期 >= #" & fd & "# And 制单日期 <= #" & ld & "# And [_Identify] <> " & e.DataRow("_Identify")
max = e.DataTable.Compute("Max(单据编号)",flt) '取得该月的相同工程代码的最大单据编号
If max > "" Then '如果存在最大单据编号
idx = CInt(max.Substring(12,4)) + 1 '获得最大单据编号的后四位顺序号,并加1
Else
idx = 1 '否则顺序号等于1
End If
e.DataRow("单据编号") = bh & Format(idx,"0000")
End If
End If
End Select