Conditional add route if BGP route is recieved

I need to add route to local route table based on if the router received specific route in BGP feed.

Actually, out ISP sends only a default route in the feed, and I need to add some more specific based on fact we still see this ISP feed at all.

Seems it can be solved but I miss the idea of how can I do that in 7.x (7.8, acually).

Plase advice!