// ------------------------
function birthday_ (_elm) {
// ---------------
	var f = _elm.form ;
	
	var s = _elm.name.split("_")[0] ;

	if (f[s + "_day"].value != "-1" && f[s + "_month"].value != "-1" && f[s + "_year"].value != "-1") {
		f[s].value = f[s + "_day"].value + "/" + f[s + "_month"].value + "/" + f[s + "_year"].value ;
	} else {
		f[s].value = "" ;
	}
}