Hi,
This is a 100% custom modification and unfortunately we don't provide free support or step-by-step instructions for custom coding modifications.
You may purchase premium support:
www.flexiblewebdesign.com/premium-support
and let us take care this modification for you directly on your website though.
TIP: The PHP file to make this modification is:
/templates/flexible_asymmetric/html/com_virtuemart/productdetails/default.php
or
/templates/flexible_asymmetric/html/com_virtuemart/productdetails/flexv2.php
(Default.php or flexv2.php, depends on what layout you are using currently for the product details page)
Regards.
Support