[Trigger] Simple spell request

[Dinodin]

I need a spell for my map that works like this when used: and knockbacks all enemy units around the Hero within a 350 AoE with the distance of 300 and then gives the knockbacked units a 30% chance to miss attacks for 3/4/5/6 seconds. This seems to be a kinda simple spell to do but I have no idéa how make it so please someone help!