Help w/ Unit Comes Within Range Event

I'm making a map where I want to use this sort of event. I've never really used it before but I've seen it many times and thought I could just use it easily. However... It's being a pain in the neck because it's not allowing me to use unit variables for the unit that it comes in range of... This is quite the problem as I have set up something that I thought would be ok if I did this. Does anyone have any idea how to get around this or how to maybe do it another way because I really can't figure anything out right now... Any help would be nice. Thanks.

Wehn you make the trigger that uses this event, don't put any events.

At the start of the game, pick every unit that is supposed to trigger the 1st trigger and add the event for the unit using the "trigger - add event" action.

Thanks - the add event thing worked fine when I put it in the right trigger once the unit was spawned.