Check String comparison in VFP

SET ANSI ON
SELECT Sales.* ;
   FROM Sales ;
   WHERE iSaleID IN (SELECT TOP 2 iSaleid FROM Sales ORDER BY cInvoiceNo DESC)

>
>I have a query like this:
>
>

SELECT Sales.* ;
>   FROM Sales ;
>   WHERE iSaleID IN (SELECT TOP 2 iSaleid FROM Sales ORDER BY cInvoiceNo DESC)

>
>The problem I'm having is due to the fact that if I have invoices entered with cInvoiceNo from "1" to "11", I want Invoices "10" and "11" to be returned, but I'm getting Invoices "1" and "11". So I really want to do something like this:
>
>

SELECT Sales.* ;
>   FROM Sales ;
>   WHERE iSaleID IN (SELECT TOP 2 iSaleid FROM Sales ORDER BY PADL(cInvoiceNo, 11) DESC)

>
>but of course that gives me a syntax error.
>
>Any ideas what I can do? I have no control over the invoice numbers as they are being returned from QuickBooks.
>
>Thanks,