>If you need to fetch all the reports (I am assuming that the max range is from 1 to 99) then following should work as long as you have EXACT turned off.
You may try using the paren's as shown to tell VFP to evaluate that before running the SQL.
SELECT *;
FROM ofax!orderitems;
WHERE Orderitems.report_num=(?cOrder_ID+"-") ;
ORDER BY Orderitems.report_num