Frustrating angle....

I have an angle that's coming in from an external field backwards... here's what I mean:

Instead of going upwards from 1 toward 360, it goes the other way, back down to one. What can I use as an expression to get the reverse? It's 3 in the morning, and my mind is escaping me.

Thanks!

Maybe [desired angle]=360-[your problem angle]?

Thanks - worked like a charm.