It may be your code is off..
Here is a sample of code we use when looking up orders by PO#.
C+ DECLARE OHBPO CURSOR FOR
C+ SELECT OHORD#, OHBTKY, OHSPO#, OHENTD, OHHOLD, OHFF3, OHSM
C+ FROM OH
C+ WHERE OHHOLD = 'E' AND OHFF3 <> ' '
C+ AND OHSPO# LIKE '%' concat Trim(:INPO) concat '%'
C+ AND OHBTKY = :INCUST
:INPO is our screen parameter