You'll have to use #define just like that. A word of caution, though: You'll have to be careful how you use it, since it matters whether this is on a line by itself or not. If you use this in an if(), then this won't work:

But this will:

It has to do with the way BYOND handles the semicolon. Unfortunately putting braces around the code right in the #define will only make things worse, whereas in C they'd be just fine.

Lummox JR