Batch File SUBST command but only remap for current process

Question

I have a jenkins job that executes a batch file. Due to some path length issues, I need to remap the jenkins working directory to a drive name using the SUBST command. The batch file looks something like this:

@echo off
REM Map working directory to a virtual drive P:
subst P: .

REM Save the original working directory so we can pop back out after we're done
pushd .
cd P:

REM *DO STUFF*

REM Pop out of P: and back to original working directory
popd

REM Unmount P: so it can be reused for future jenkins jobs
subst P: /D

I need to unmount because SUBST changes are global for a given user. The problem is what if the jenkins job is inside the "DO STUFF" and someone cancels the job? Then the job wouldn't have a chance to execute "subst P: /D" and therefore P: will never be unmounted. And batch doesn't support any kind of sigtrap. Is there another batch command that does what SUBST does but local to the calling shell?