Need Help to lvl up a Ability W/O Training

Need Help to lvl up a Ability W/O Training

Right now i'm working on a new map. everything is just fine and dandy but only 1 problem. i cant get an ability to lvl up each time i buy it. it always stays at lvl 1 and i have no clue why. so can any 1 help me in any way?

hey ok what you do is
event
unit buys item
condition
boolean condition
action
hero- increase Ability of ???

that should work for you it will be simple