How do I make a make a certain block give you a potion effect in a certain radius?

I want to make a block that gives you a potion effect, which allows you to fly, in a certain radius, but can't figure how exactly to do this. I've tried making a procedure that detects if a player entity is inside a certain radius, then applies said potion effect, but the block's On Update Tick trigger doesn't allow for procedures with the Entity tag for some reason, and I can't figure out any way to get around this, so I'm stuck. Any ideas on how to do this?