i am more interesting in running a simulation on the source code and breaking / stopping at various points to examine the values of variables, will it do that ?
It certainly will and more beside. For instance you can also trigger breakpoints on hardware events (either digital or analogue).

The downside for you is that there is no way - somebody correct me if I'm wrong - of moving a schematic from Altium to Proteus. Proteus does of course have the ability to duplicate most of Altiums functions - maybe enough for you needs?

BTW one problem I found with Proteus/PBP is include files. Proteus just doesn't like to single step into them - easy work round tho.

The procedures to link PBP to both Proteus7 and 8 are available.

George