Snowball Fight Help

[Turnip]

Hello,
I am making a Snowball Fight type map, and I need to know how to do the throw snowball trigger. How do I make it have a smooth motion going up, then down? How do I make it go over your units or allies units or buildings, but stop in mid air if an enemy unit goes infront of it? Here are a few pictures of what I mean:

~After the war, the only true wisdom came from turnips.~

 

[Aw2k6]

Try basing the 'Throw Snowball' Spell off of a spell that already arcs, a mortar-type spell. (I'm more trigger familiar than I am with the game, no spells come to mind, but they probably will for you)

 

[Ozzdog]

Just change his regualr attack: change weapon type to artillery in the unit editor, and import a custom snowball model, and change his projectil art to the snowball. Or does it HAVE to be an ability, rather than an attack?

 

[Turnip]

It has to be an ability.