Pseudo-atom for halogen bonding

GROMACS version: 2023.1
GROMACS modification: No
I would like to ask how can i introduce a pseudo-atom at a molecule of my choice, while generating my system via charmm-gui.
The purpose is to compare my new simulations and study the role of halogen bonds being formatted.
Is there any way to introduce a pseudo-atom or should i parametrize my force field?
Thank you