Bending of a chain

Hi,

I have a question which might sound trivial, but I couldn’t figure it out. I have a polymer chain made of multiple beads connected with springs. I want to bend that chain like a cantilever beam. I was successful in doing this using velocity boundary conditions. I fixed the left most two atoms of the chain and I applied a velocity in the y-direction to the the right most atom while allowing it to move freely in the x-direction. My question is how to do such simulation with force boundary condition. I have tried set force command but it is not working.

Thanks.