Now I have this but unsure what to do next to get it to work
<form name="InsoleCart_1_ATC_0" method="POST" action="<?php echo $_SERVER["PHP_SELF"]; ?><?php echo (isset($_SERVER["QUERY_STRING"]) && $_SERVER["QUERY_STRING"] != "")?"?".$_SERVER["QUERY_STRING"]:""; ?>">
<input type="hidden" name="InsoleCart_1_ID_Add" value="0" >
<input name="InsoleCart_1_Quantity_Add" type="text" value="1" size="4">
<select name="InsoleCart_1_Price_Add" onChange="onChange="document.InsoleCart_1_ATC_0.<Size>.value = ">
<option value="2.99" selected>75cm Fine-3mm</option>
<option value="2.99">75cm Heavy-5mm</option>
<option value="3.50">100cm Fine-3mm</option>
<option value="3.75">100cm Heavy-5mm</option>
<option value="3.75">120cm Fine-3mm</option>
<option value="3.75">120cm Heavy-5mm</option>
<option value="3.99">140cm Fine-3mm</option>
<option value="4.10">140cm Heavy-5mm</option>
<option value="4.40">180cm Heavy-5mm</option>
</select>
<input type="hidden" name="InsoleCart_1_Size_Add" value="" >
<input type="image" value="Add to Cart" name="InsoleCart_1_ATC" src="../../WA_eCart/Images/Pacifica/Btn2_EN_addtocart.gif" border="0">