Another coding resource, it that helps the task any more. Sorry guys, I'd do it myself, but I don't know how. 
Code:
startTime = getTimer();
minTimer = startTime;
n = 1;
freq = 333; // <- 3 beats per second or 180 bpm
metroI = setInterval(metroF, freq, freq);
function metroF(compensatedFreq) {
errorTime = getTimer()-startTime-freq; // this is a correction factor used 2 lines below
clearInterval(metroI);
metroI = setInterval(metroF, compensatedFreq-errorTime, compensatedFreq-errorTime);
if (getTimer()-minTimer>=60000) { // this allows a test of the number of beats recorded in about 1 min
clearInterval(metroI);
trace(n);
}
startTime = getTimer();
n++;
}