Question set a variable to a specific room

I'm in room 100 and my trigger (just a simple snippet here):

set testvar = 1
global testvar

will set testvar to a room with a value of 1 to room 100.

BUT 

How would I set testvar to a value of 1 in room 3000 when the trigger is in room 100?

Thanks!

Wow, that took a little while to remember: Note that you need to put the room number in a variable, or it won't work.