how to run a cmd.exe batch file in a sub shell

I have a batch file that I usually invoke like this:

 longjob.cmd >result.txt 2>&1

This works fine, but the script changes directory during its execution leaving my shell in that directory - which is a nuisance.

Is there a way to run the command within a sub-shell - while still allowing the output to be captured ?

I have tried

cmd longjob.cmd >result.txt 2>&1

which just sits waiting for an exit command.

Also I tried

start longjob.cmd >result.txt 2>&1

which does run the script, but in a new window and all output is sent to that window instead of the file.