function updateField(elFrom, elTo)
{
    var elFromName = elFrom.name;
    var elFromValue = elFrom.value;
    
    var elToName = elTo;
    var elToValue = $('ad_' + elTo).value;
    
    var base_url = $('BASE_URL').value;
    var time = $('T').value;
    
    // ajax request
	new Ajax.Request(base_url, {
		method: 'get',
		parameters: 't=' + time + '&P=form_fields&elToName=' + elToName + '&elToValue=' + elToValue + '&elFromValue=' + elFromValue + '&elFromName=' + elFromName,
		onSuccess: function(resp) 
		{
			$('ad_' + elTo).update(resp.responseText);
		}
	});
}