A: In the Eastern District of Michigan the standard plan requires you to turn over your refund. It is not a matter of the trustee grabbing it.
The good news is you can always amend your plan to account for change of circumstances. Show expenses for any un-budgeted event such as job loss and you will probably be able to keep your refund or some part of it.
You need to talk to your attorney (if you have one) about your various options.