Hi,
No it is not possible except a Virtuemart Core hack. Which is not recommend by us. Beside since what you are asking is a custom modification, we don't give tutorial/solution/instruction for custom modifications. Try
forum.virtuemart.net
Keep this in mind; Modifying or changing any file in these folders:
/components/com_virtuemart/
and
/administrator/components/com_virtuemart/
Are considered as Virtuemart Hack. It is not a good thing and eventually (once you upgrade your Virtuemart) your changes will be retrieved back to original.
Regards.
Forum Support.