Critical Path for a Subset of Schedule

Hi,

  Can critical path be seen for a subset of schedule instead of entire schedule ? 

I have a program schedule, which runs for over 3 years. The entire schedule is broken down into sizeable "Work Packages" and there are deliverables & milestones for every work package.  The future work packages are just place holders and the work packages which have their deliverables in the next 4 months are active work packages. There are multiple active work packages and they do not link to each other i.e. they are not dependent on one another.

Only for these active work packages, detailed tasks are identified and their dependencies are linked to the work package's deliverables & milestones etc. 

These active work packages are not linked to each other. 

Also, often these work package's has their 1st task to start on a particular date i.e. they have "Must start on" constraint and then the subsequent tasks are identified and linked to each other.  

Now I need to find the critical path for these individual work packages i.e. which of the tasks within the work package when delayed will delay the milestone of that particular work package. 

Critical path filtering & highlight feature works when the entire schedule is linked and these give the critical path for entire schedule. 

But how do I find the critical path for a subset of schedule i.e. in my case, critical path of the work package(s) ?  

One crude way is to copy paste a work package on another .mpp file, and use filter / highlight critical path feature.  Another way is to make each work package as a sub-project with independent .mpp file and have a master schedule linking all sub-projects. 

I don't want to do both of these due to level of complexities involved. 

So how do I find a critical path for a work package alone ? 

Any thoughts please ?