How do I persist an "unit" to a variable?

I want to select a "worker" and then the player select possible things to build... but how I will now witch worker the player selected? There is no "sprite" variable for me to set.

I thought to set a variable to all workers "selected", but every time I need to do something with the selected one... I need to do a foreach, this is possible not the best choice...

There other way to do this type of thing?

wilsonglasser: Check out the manual entries on UID, which is exactly what you're looking for.