Knockback Effects

Hello again. How would you create a knockback effect? I've searched several forums and I haven't been able to find anything relevant. (This is the second part to a spell I posted earlier)

Edit: Added very detailed drawing




Thanks advance!

Vile has some Knockback Functions posted in the resource section of this site.

Thank you to both you and vile! I'm suprised I didn't find that myself. >.>;