I am displaying my items in columns, and I want to create a drop-down box so the user can sort by price etc.

So far I have the following code in tpl_index_product_list.php:

<form name="sorter" action="http://www.dreamofrussia.com/index.php?main_page=index&cPath=7" method="get"><select name="sorter" onchange="this.form.submit();">
<OPTION SELECTED value="">Sort by...
<OPTION value="&sortby=4a">Price
<OPTION value="&sortby=3a">Artist Name
<OPTION value="&sortby=2a">Size
</SELECT>
</FORM>

How can I make it so that the sorter will work for any category, ie. dynamically choose which category?

Thanks in advance.