How much would this design cost?

I'm trying to determine if the bookcase slides only on the casters or it there is a way to suspend it from a track. I believe this picture shows the case on casters and that it would roll away from the front of the Murphy bed. I'm looking or suggestions as to how to suspend a bookcase in front of the Murphy bed, then slide it out of the way when the bed is needed.

We suspend 2 bookcases on tracks and they glide away from the front of the bed. It's called a library bed. We sell hundreds of them. www.OntarioMurphyBeds.com