[Trigger] pushing a group of units

[MGCǂSpectre]

Who can tell me triggers to make after an ability with targeting ground (such as cluster rockets, flame strike) is cast, the units within 400 of target point of ability being cast to be pushed away. I can make it to the point where I can select exactly the group of units in the range of the ability to 'suffer'. How can I make the pushing of this group of units? It should be in the opposite direction of the ability, in other words the units to move in line away from the target point.

 

[chenlimin]

Had to use a kockback system, but most was done in Jass or has some Jass.