Help: Some kind of "ignore this unit" spell...

Hello.
Id like to make a spell, that causes all units within X to ignore the target for Y seconds. However, other units that join the battle can attack the caster and if the caster itself attacks a unit with the spell on it, it removes the spell from that unit.
I cannot think of a way to do it without JASS (yepp, no JASS). Any ideas how it could work? An idea is all I need. The problem is how to have single units ignore a possible target.

Thanks for any input.

Why not add all the units within the range of the casting unit into a unit group. Set a boolean variable to true. After doing that have a trigger that checks when a unit is issued an order. Conditions should check if the unit is in the group = to true and if the boolean variable is equal to true and if the order is equal to attack. Then the actions should order the ordered unit to follow target unit of issues order. Have a timer run when the unit casts the spell as well and when the timer runs out remove the units from the unit group and set the boolean to false.

Hmm.. but they should attack other units

Then add a unit variable that sets the caster. Then add a condition that checks if the target of issued order is = to the caster. Then set casting unit to null after timer.