Source control for multiple projects

Question

I've worked with SourceGear Vault for sometime for source control but I've run into a problem - which is going to be all the more common.

I have a visual studio solutions that looks like so:

-Main solution
      - Web App Project
      - Shared Class Library 1
      - Shared Class Library 2

The problem is that I can only bind the solution to one repository, however the class libraries are shared, they need to be used by multiple solutions.

Is there a source control solution that anyone knows of that will allow for a solution to contain multiple projects, all bound to different repositories?

Thanks in advance Al