Custom bear mob spawn only below beehive?

[verbal atlas]

How can I use the spawn rules to make my custom bear mob spawn only Under beehive blocks? (I know how to make him spawn only On grass, but Under is trickier!) Thanks!

[hollow pier]

could maybe use the "minecraft:entity_spawned" event and run a /testblock command or /execute at @s if block ~ ~+2 ~ bee_nest run

I know it's not using spawn rules, but it is best method I know of