setInterval + dynamic txtfields = don't work!

hello all,
i’m having trouble using setInterval() to delay some textfields. they textfields are dynamically generated and i can animate the just fine using a for loop or an if statement…i just can’t figure out how to get setInterval() to delay the iteration…

 
anim = function(a){
for(a=0; a< _global.bldgFacts; a++){
     this.holder_anim["facts" + a]["factstxt" + a]._x +=(400-this.holder_anim["facts" + a]["factstxt" + a]._x)/20;
   }
}
 
this.onEnterFrame {
a=0;var myInterval(anim, 5000);
}

i’ve tried a billion different things a billion different ways and haven’t done anything but confuse myself!

thanks!