How to create base build and two simultaneously child builds?

Question

Using visual source safe,

How to create a base build and on top of that two inherited new child builds of c# project.

Base Build - Base Project - Base source version. [Should be able to modify source file and it reflacts in child builds]

1. Child Build - First Project
2. Child Build - Second Project

I can able to modify individual source code of both child builds and also base build.

If i change base build any source file then it should reflact to child build also.

Is this possible with VSS? if yes how can i achieve it

If any other source control provide this kind of facility then let me know.