I'm sorry I misunderstood the boundary issue. We should shift all boundaries in proportion to the arguments of SPHOME as follows. (before correction) IF X<0 THEN X=0 IF X>385 THEN X=385 IF Y<18 THEN Y=18 IF Y>225 THEN Y=225 (after correction) IF X<8 THEN X=8 IF X>393 THEN X=393 IF Y<26 THEN Y=26 IF Y>233 THEN Y=233