function func_qty(var_id,var_type,var_portion) {
	if (var_type == "people") {
		people = parseFloat(document.getElementById("form_" + var_id + "_people").value);
		if (isNaN(people)) {
			document.getElementById("form_" + var_id + "_people").value = "";
			quantity = 0;
		} else {
			quantity = people * var_portion/1000;
		};
		document.getElementById("form_" + var_id + "_quantity").value = quantity;
	}
	if (var_type == "quantity") {
		quantity = parseFloat(document.getElementById("form_" + var_id + "_quantity").value);
		if (isNaN(quantity)) {
			document.getElementById("form_" + var_id + "_quantity").value = "";
			people = 0;
		} else {
			people = Math.floor(quantity / var_portion*1000,2);
		};
		document.getElementById("form_" + var_id + "_people").value = people;
	}
}