function submitenter(myfield,e)
{
var keycode;
if (window.event) keycode = window.event.keyCode;
else if (e) keycode = e.which;
else return true;

if (keycode == 13){
	return checkInput(myfield.form);
}
else
	return true;
}

function checkInput(theForm){
	var chiave_reg_exp = /([a-zA-Z0-9])/;

	if ((theForm.chiave.value==0) && (theForm.chiave.value.length<=0)) {
		return false;
	}
	if (theForm.chiave.value.length > 0){
		if (!chiave_reg_exp.test(theForm.chiave.value)){
			return false;
		}
	}

}