[Help!] Small Basic bug

Hello… I am have been coding for a long while now, and have come into a error with a section of my code. I have been trying to make jumping pyisics for a mario like scroller. Having tried for 3 years now i have finnaly cracked the code ; ). But the problem is that when i put the jump code into a key down sub, it doesnt jump. However, it functions perfectly as a plain for loop.

plz help…

the download code is here --> ZKC804

when you un-comment the commented lines of code it will not work anymore…that is what i need help fixing… (i commented some of the code so that i didnt have to upload 2 programs)

thank you !!!