主题：自动编码序号如何修改

Dim r As Row = Tables("表A").Current
If r.IsNull("制单日期") OrElse r.IsNull("工程代码") Then
    r("单据编号") = Nothing
Else
    Dim d As Date = r("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 = r("工程代码") & "-" & Format(d,"yyyyMM") & "-" '生成编号的前缀
    If r("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 = '"& r("工程代码") & "' And 制单日期 >= #" & fd & "# And 制单日期 <= #" & ld & "# And [_Identify] <> " &r("_Identify")
        max = Datatables("表A").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
        r("单据编号") = bh & Format(idx,"0000")
    End If
End If