compute pair/gran/local of atoms in a defined region

Hi Experts,

I can´t solve the task to write the contact forces between particles in a defiend region. I tried it with:

region comp block -0.075 0.075 0.0 0.075 0.015 0.03 units box

group comp_group region comp

compute Force comp-group pair/gran/local id pos force

My Problem: As per documentation: "The region style puts all atoms in the region volume into the group. Note that this is a static one-time assignment"
When the atoms move further in the next steps, they will leave the region but will not leave the group.
I tried it with some loops and with deleting and uncomputing these commands, but this leads always to error messages.

Could you give me a command or a solution way to solve this issue? I´m working with liggghts V3.8.0.
Thanks a lot,
Nils