Fading new incrementing

Hello, heres the prob. I’m trying to get a mc named viewer to fade in when a user clicks a button by using the code in red. This works fine when the user clicks the first time, but if the user clicks numerously for a duration of time the fade slowly disappears (doesn’t happen anymore). Any ideas.

Also, if I put in a trace command and look at the alpha, it doesn’t actually increment by 1 for some reason. I can’t figure out why.

Thx in adavance.

[COLOR=DarkRed]viewer._alpha = 0;

var ninterval:Number = setInterval(fade, 1);

function fade():Void {
if(viewer._alpha < 100)
{
viewer._alpha = viewer._alpha + 1;
}
}[/COLOR]