Help with a Custom Spell

I want to make a custom spell prolly through JASS. Its called Freezing Field i want to damage and stop all units within a certain range of the caster and have the graphic of the frost wyrm's attack freezing breath attack on each affected enemy unit.

I wanna learn JASS if I can REALLY make spells like this...

O_o

Sounds cool, but I havn't a clue of how to do it, sorry.