Need help with a Destructible(Tree) targeting spell..

Hello,
I'm trying to make a dummy spell for an item(An Axe) which targets a single tree. i've already tried various spells to modify them to the status I need, e.g. making it possible to "chop" the tree with several uses of the ability (The damaging part will be done through a trigger).
But seems I'm kinda out of ideas right now, the sentinel ability does only work 1 single time, after that it gives a "There is already a Owl on that tree" error, using the War Club Ability resulted in an instant death and a modified Purge ability wanted to have a tree with an Owl(?!).

Hope somebody can help me out.
Greets

Make it based on Channel, it can target anithing, look at various threads on this site, they say how to use Channel.

That doesn't really work..I set it to be a unit targeting spell(In fact it isn't) and as valid targets I set trees. It still tells me "It must be a tree" while I try clicking on trees..

well, base the spell on owl and then, with triggers, have dummy casters purge the tree, so you can then "owl" it again.

Ah, thanks a bunch, got it now, I didn't even know you can purge trees