为什么在Access数据库中，为什么会出现断号？

Select Case e.DataCol.Name
    Case "客户名称","客户类型","录入日期"
        If dr.IsNull("客户名称") OrElse dr.IsNull("客户类型") OrElse dr.IsNull("录入日期") Then    \'其中有一个是空时
            dr("客户编号") = Nothing
        Else
            If dr("审核") = False  Then
                Dim flag As Boolean = False
                Dim d As Date = e.DataRow("录入日期")   \'提取开标日期的年份
                Dim bh As String = Format(d, "yyyy")
                Dim lb As String = "CH" & bh & "-"
                Dim bhs As List(of String) = e.DataTable.SQLGetValues("客户编号", "客户编号 Like \'" & lb & "%\' And [_Identify] <> " & dr("_Identify"))
                For i As Integer = 1 To bhs.Count
                    If bhs(i-1) <> lb & Format(i, "0000") Then
                        lb = lb & Format(i, "0000")
                        flag = True
                        Exit For
                    End If
                Next
                If bhs.Count = 0 Then
                    lb = lb & "0001"
                ElseIf flag = False Then
                    lb = lb & Format(bhs.Count + 1, "0000")
                End If
                e.DataRow("客户编号") = lb
                e.DataRow.Save()
            Else
                Return
            End If
        End If
End Select