Modify VirtueMart plugin

I am using Joomla 3 / VirtueMart 3, but bypassing the standard virtuemart checkout and using an external cart that uses a form-post solution - below is the code I replaced the 'add to cart' virtuemart code with -------------------------------------------- <form action="[login to view URL]" method="post" name="form1" target="_self"> <input name="userid" type="hidden" value="CUSTOMER NUMBER" /> <input name="product" type="hidden" value="<?php echo $this->product->product_sku ?> <?php echo $this->product->product_name ?>" /> <input name="price" type="hidden" value=" <?php echo $this->product->prices['basePrice'] ?> " /> <input name="qty" type="hidden" value="1" /> <!--<input name="return" type="hidden" value="WEBSITE/<?php //echo $previous ?>" />--> <input name="return" type="hidden" value="<?php echo fgcgetPageURL(); ?>" /> <input name="Submit2" type="submit" value="Buy Now" /> </form> --------------------------------- this works fine on regular product details pages, and I have modified the 'simple product snapshot' to use this solution as well. Now I need to have the catpro product content plugin (I can supply - see attached, or see [login to view URL] ) modified to use this post type instead of the standard VirtueMart add to cart