upgrade btn...

Hi! need guide to create a upgrade kind of btn... so far this is the situation:
i create a btn to use for upgrade but it out weird coz if i hv lot of money to upgrade more than a lvl, it automatic upgrade like 3 lvl on a single click... i want it to upgrade once per click not multiple time per click...
exp:
this is what i want it to happen
time slow length 1 sec <buy>(1 click) ---> time slow length 2sec
but now if u have enough to upgrade more than once...
time slow length 1 sec <buy>(1click)---> time slow length 3 sec
Help?
i create a btn to use for upgrade but it out weird coz if i hv lot of money to upgrade more than a lvl, it automatic upgrade like 3 lvl on a single click... i want it to upgrade once per click not multiple time per click...
exp:
this is what i want it to happen
time slow length 1 sec <buy>(1 click) ---> time slow length 2sec
but now if u have enough to upgrade more than once...
time slow length 1 sec <buy>(1click)---> time slow length 3 sec
Help?
Comments
Rule
if button is Pressed && game.money >= game.SkillCost
--> game.skillLevel = game.skillLevel+1;
--> game.SkillCost = game.SkillCost+ (needed additional money for the next upgrade)
Rule
if game.skilleLevel = 1
--->add upgrade here
if game.skillLevel = 2
-->add upgrade here
etc....
mangaroo --> Really? Sry! will try to do better next time! (p.s. bad at english