When we programmed out cash drawer we did it like this:

PROCEDURE open_drawer
SET PRINTER TO lpt1: && (or lpt2:, lpt3:, \\pc\printer, etc.)
SET PRINTER ON
? &string_to_open_the_drawer && where string_to_open_the_drawer = the
SET PRINTER OFF && string for the particular cash
SET PRINTER TO && drawer given by the manufacture
RETURN

This opened the cash drawer on the lpt port...

Good Luck