prototype - triggering each onchange event

I'm wondering if the following is possible, so far I got 开发者_StackOverflowit to work, however, I get three alerts since I have three text-boxes that get set at the same time. I would like to alert the new date only once.

var x = 0;
$$('.class').each(function(el) {
    $(el).observe('change', function() {
        d = ($('y').value + $('m').value - 1 + $('d').value);
        if (x == 0) alert(d)
    });
});

Only for you Mike am posting my comment as answer . You can now accpet it as answer :-)

use any flag variable. on first alert set flag. if flag set dont alert. this is just js. dont know any other prototype way