Yes, JomGenius to the rescue...

Let's assume that you're going to identify the categories directly, rather than ancestor categories. The following example will display on category pages (where the category is the one listed in each case) and also on product pages, where the product is in the category listed.

$vm = JomGenius("virtuemart");
if ( $vm->check("category_ids = 3, 4, 5, 6") ) return XXX;
if ( $vm->check("category_ids = 7, 8, 9") ) return YYY;
return ZZZ; // any page on the site not matching the previous 2 lines

Replace XXX, YYY and ZZZ with the appropriate module ids to return in each case.

Hope that helps,
Stephen

Ahem, yeah, looking good!

Stephen