Use the VS.NET Get Version action to retrieve the assembly version from a VS.NET project or AssemblyInfo file. Or see this post if you need to retrieve the version from a compiled assembly:
http://www.kinook.com/Forum/showthread.php?threadid=403
Use the Make VS.NET action to update the File version of a VS.NET project, solution, or AssemblyInfo file. See this post for how to handle differing file/assembly/product versions:
http://www.kinook.com/Forum/showthread.php?threadid=371
See the help topics on those actions for more details, and/or the samples that use them (GetProjVer.bld and VStudio.bld).