Regarding restraining molecule between the graphene sheets using colvars

Dear all,

I am doing MD simulation in which I want to restrict a molecule (HSS) between two graphene sheets (parallel to each other in xz-plane) separated along y-direction, and whose center of mass is located at origin. Each graphene sheet is of size 14 Å in length and width.

I am trying to implement this with colvars, please find my colvars script below, any help will be appreciated