Parabolic trajectory problem

Dear readers,

I have an extremely complicated mathematical problem which I just can’t get my head around.
What I want is a system that makes one person aim at another person while his cannons bullets fly like mortars, so in a parabolic curve. In this situation I know:

  • The distance between me and my enemy
  • My cannons firepower
  • Gravities strength

Of course I know more, but I think these are the only relevant things.
I found a wikipedia article explaining my problem, but I haven’t done university in maths (yet), so I don’t understand anything about it: http://en.wikipedia.org/wiki/Trajectory

If the effect I want to have is not clear then here’s an example: http://dan-ball.jp/en/javagame/ranger/ The archer (Sniper) in this game (Stick Ranger) can hit the enemies with his bow in a certain arch. I want that too!
**
All I need is to know is the angle needed to get the cannonball to hit my enemy! **
Ow…It should be done in AS2…

I really hope someone can help me with this!

Cheers,

~Sir Realism