[Tontinuk]

Ive done this now with the following

var value = parseInt(product_option_value("MUH"));

var value2 = parseInt(product_option_value("MUW"));

var newquant = (value * value2);

document.getElementById("product_avail").value = newquant ;

var qtybox = parseInt(document.getElementById("product_avail").value);

if (  qtybox !== newquant) {

alert("Sorry, the quantity does not match the mailbox bank sizer ytybox " + qtybox + "newquant " + newquant);

return false;

} 

the problem with this is it only changes the quantity when the add to cart button is pressed thus calling the checkoptions routine,

can I call the routine when either of the dropdowns are changed and if so how and where should I put the code.