Need some help with bell training

I have a 1 year old corgi. I've been trying to teach him to signal me when to go out using bells.

I've gotten to the point where he rings the bells every time it's his scheduled potty break, but I think he's inadvertently learned that ringing the bell = getting my attention instead of going outside to the yard. He'll ring the bell on his own, I diligently go to open the door, but he just stares at me instead unless I leash him up and take him outside myself.

What should my approach be to get him to learn that bell = going outside instead?