Sorry to be asking so many questions but after attempting to find the solution I see no alternative. The attached code illustrates my two problems. 1. Line 53 error index out of bounds I find baffling. Removing line 73 removes the error but of course the result is incorrect. 2. The AddSprites sub has slowed the action by say, 50%. The sprites are static and although of course repainted, I cannot see that it is likely to be the cause. Removing line 50 recovers the speed. Any help appreciated.