老师 能帮我编个自动编号程序吗？

收据的编号我想用日期按月编

老师我编了 但是出错

If e.DataCol.Name = "日期" Then
    If e.DataRow.IsNull("日期") Then
        e.DataRow("编号") = Nothing
    Else
        Dim d As Date = e.DataRow("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)
        Dim ld As Date = New Date(y,m,Days) 
        Dim bh As String = Format(d,"yyyyMM")
        If e.DataRow("编号").StartsWith(bh) = False 
            Dim max As String
            Dim idx As Integer
            max = e.DataTable.Compute("Max(编号)","日期 >= #" & fd & "# And 日期 <= #" & ld & "# And [_Identify] <> " & e.DataRow("_Identify")) \'取得该月的最大编号
            If max > "" Then 
                idx = CInt(max.Substring(7,3)) + 1  
            Else
                idx = 1
            End If
            e.DataRow("编号") = bh & "-" & Format(idx,"000")
        End If
    End If
End If

运行错

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