Problem with llcollision for Avatar Detection inside phantom prim

Hey folks,

I created a phantom prim, a 5x5x5m box (llVolumeDetect) as i need to know whois inside, so
llColision wont work.

I now want to check, if an Avy is inside this prim. I use collision_start and -end events.

Works great when pple walk inside the prim and then walk outside.Only has one small glitch. If someone inside the prim takes a TP out of it, the llCollision_end doesnt trigger. And my prim still "thinks" someone is inside.

Maybe a quick llSensor on a timer set off by collision_start to check say every 30 seconds