Display timer

hi guys,, I want to make timer for the game I make. I already make the timer and it works well. the problem start when I add frame/ scene before the timer, the timer is hidden. can you solve this problem for me please.

I used this code for my timer

Actionscript Code:

//timer
timer = 0;
countup = function(){
    timer++;
}
countupInterval = setInterval(countup,1000);

and at next frame where I want to display result of the timer I used

timer_txt.text = timer;

here I also attached my file. please solve this problem for me...