function objectByID(id) {
	var returnVar;
	if (document.getElementById) {
		returnVar = document.getElementById(id);
	} else if (document.all) {
		returnVar = document.all[id];
	}	
	return returnVar;
}

function activateFree(textfield) {
	var radio = objectByID("radio.amountfree");
		
	if(textfield.value) {
		radio.checked = 'checked';
	}
}