Unit Detection Trigger

I'm currently trying to make a trigger that orders wards to automatically cast spells when units are nearby. I'm having a lot of trouble as to how to make it detect units and be multi instanceable. Any words of advice?

Wards.... Units with the ward classification. I think that it's the problem.

When a unit has the ward clasification, it has its command card completely disabled, only "smart" function (right clicking on unit) will work, so if the unit has spells, they will be disabled by the ward classification.