DPS Counter

I'd like to set a DPS meter up through adding up dealt damage into a variable each time the "damage message" trigger fires.

How could I solve the time calculation problem, however?

Is there a function that will return the time passed between two calls or something?

os.time() will return the time in seconds.

Also see os.difftime().

You can find these things out by typing Shift+Ctrl+Alt+L and then type "time" into the search box.