Since you are dealing with building specifically you may want to replace your batch file with an MSBuild file. For example:
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<ItemGroup>
<SolutionsToBuild Include="MySolution.sln"/>
<Projects Include="Proj1.csproj"/>
<Projects Include="Proj2.csproj"/>
<Projects Include="Proj3.csproj"/>
</ItemGroup>
<Target Name="BuildAll">
<!-- Just executes the DefaultTargets (Build) -->
<MSBuild Projects="@(SolutionsToBuild)"/>
<!-- Call Rebuild if you think its not building correctly -->
<MSBuild Projects="@(Projects)"
Targets="Rebuild"/>
</Target>
</Project>
Then you just invoke msbuild.exe on this file with:
msbuild.exe Build.proj /t:BuildAll
Since you said that you want to build specific projects after the solution is built just put those into the Projects ItemGroup as shown and use the MSBuild task to build them after the solution has been built. I've specified the Rebuild target to make sure you get a clean build.