Exclude tables from shared_buffers in postgres

Is there a way to exclude tables from being added to the shared_buffers? I've looked at the space used by the tables and those which use the most are not really relevant for us at the moment. There are some tables which we only write to but don't need to have fast read-access at the moment. For a few tables we would like to keep the latest rows in the memory. If we could only mark these tables to be added to the shared_buffer that would allow us to use the memory on the machine much more efficiently.