Most supplemental life insurance plans offered through your job provide term coverage. This means it is only in effect for a limited period of time — typically until you leave the job — and does not offer a cash value that you can cash out at a later time.
But you may be able to purchase a permanent supplement life policy — through a private insurer if your employer doesn’t offer one. This will allow you to build up a cash value in the policy which you can later borrow against or cash out.