Contact forces for multisphere particles

Hi,

I am using glued-spheres particles to do my simulations and I want to calculate the contact forces between these glued-sphere particles.

I know I can get the contact forces between individual spheres using 'compute 1 all pair/gran/local' command but I want to treat one glued-sphere particle as a single entity and when two glued-spheres will be in contact there will be multiple spheres from both the glued-spheres in contact. I want the summation all the forces acting on the individual spheres for that contact pair.

My explanation may be slightly confusing here and therefore I have tried to explain it using an image attached with the topic.

Thanks,

Rohit Kumar