Of course. Depending on what you want to use as a base spell for the healing, you can use triggers to do this. If you want to make a spell like Holy Light, here is the trigger.
Event - An unit starts the effect of an ability
COnditions - (Ability being cast) Equal to "Your ability"
Actions - Unit - Set life of (Target unit of ability being cast) to ((Life of (Target unit of Ability being Cast)) + ((Max life of (Target unit of ability being cast)) * 0.10))
NOTE: You can change the 0.10 value in what you want. Still, remember that 1.00 is 100% and 0.01 is 1%. So, the percent is actually the number after the point, as long as 0 is the number before the point (except 100% which as I said before is 1.00).
Hope it helps you.