[MP2]

When the timer ends, the variable will still contain the timer's ID, so no, it won't work.

Let's see..

pawn Code:

new timer;

blahblah = SetTimerEx(..)
timer++;

public thetimerfunction(..)
{
    // Blah blah
    timer--;
}

// Check if running
if(timer) // Timer is running

You should bare in mind that you can have two timers running at once, the same function, so you don't want =1 or =0 you want ++ and --.