Just in case for the future you can do what i was suggesting...
Don't use a SQL Expression field use a Formula Field (the one with the "x-1" icon).
Right click on it and select New.
When the Name box pops up you can put whatever but for now just use Last_Year_Sales_Sort.
Hit OK.
In the formula workshop find your Customers table and double click on the Last Year Sales field to bring it into the formula.
Click on save and close. All you did here was create a field that is exactly the same as the Last Year Sales field from your table. Nothing more.
You do not even have to put it into your report to sort by it but you can if you want to see what the field is doing.
from this point follow the last post ...
Go to the Record Sort Expert (the AtoZ button next to the select Expert).
Under Report Fields their should now be a field called "X-1 Last_Year_Sales _Sort". Click on it and then click on the over arrow to move it to the sort fields box. Under the Sort fields box you can choose Ascending or Descending.
Edited by DBlank - 29 Dec 2008 at 12:48pm