function duplicate_field(field_id) {
	field = document.getElementById(field_id);
	if (field.value != '') {
		newNode = field.parentNode.cloneNode(1);
		field.parentNode.removeChild(document.getElementById('duplicate').parentNode);
		newField = newNode.lastChild.previousSibling.previousSibling;
		newField.value = '';
		newNumber = parseInt(field_id.replace(/[^\d]+(\d+)[^\d]*/,'$1')) + 1;
		newField.name = newField.id = field_id.replace(/(\d+)/,newNumber);
		field.parentNode.parentNode.appendChild(newNode);
		document.getElementById("duplicate").onClick = "duplicate_field('" + newField.name + "'); return false;";
		return false;
	}
}