dynamic group assignment in cfdem

I have a stream of particles in a fluid flow and want to write the data of paticles entering a certain region to a file. To do this I need to dynamically update the group assignments of my particles.
In Liggghts the following works fine:
run 1e5 upto every 100 &
"undump dmp2" &
"group nve_groupOut delete" &
"group nve_groupOut region regOut" &
"dump dmp2 nve_groupOut custom ${outInt} ${path}/DEM/post/dump*.out id type type x y z ix iy iz vx vy vz fx fy fz omegax omegay omegaz radius"
When using this in CFDEMCoupling, this procedure does not work. Can anybody give me a hint what's the problem and how a dynamic group assignment in cfdem could be realized.