Hello Dhruv
It is possible to create a route map that will set the community string for particular prefixes it sends to its BGP neighbors. This can be done by using the match ip route-source route-map command where the OSPF router ID is the route source.
You can then set the community of those prefixes that are sent from the desired route source (OSPF router ID) to whatever you like.
For more info on setting BGP communities using a route map take a look at this lesson:
For more info on route maps in general, take a look at this lesson:
For more info on the match ip route-source command, take a look at the NetworkLessons note on matching OSPF router IDs using route maps.
I hope this has been helpful!
Laz