This should do it as long as you don’t go above 999,999:
startCount = 0;
endCount = 500000;
countDur = 200;
s = “” + Math.round(linear(time,0,countDur,startCount,endCount));
if (s.length > 3){
s.substr(0, s.length -3) + “,” + s.substr(-3);
}else{
s
}
Dan