Using onchange event handler to alter second select list

[DubHalo]

Really can't get my head around how to achieve this:Have a form field asking for a product, these are various sizes, the second form field asks for the quantity.The stock quantity of each product is shown in the first select, I want the second select to be a maximum of the stock available so customers cannot order more than I have available.This is the first select (also linked to show custom pictures) Site is ASP\[code\]<select name="barcode" id="imageselect"> <option value>Please Select .....</option> <option value="http://stackoverflow.com/questions/12678827/322974">6.6lbs 100m -