[prototype] How to observe the value of a generated field (by AJAX)

[Guezt]

Hi @ all !

I written a small function for prototype that retrieve a new <select> input from the database (using a PHP ajax handler) and replace() the old one using responseText.

onSuccess: function(transport){$('foobar_select').replace(transport.responseText);},

But, is there a function that can says "if the select input was replaced then..." ?
or "if the default value of the select input changes then..." ?