I have had to put my elder in the back seat with child safety locks due to her opening the doors and trying to run off.

I got the door locks part problem. She just thinks that she can get out anywhere and hitch a ride with strangers. I do have music she likes on all the time. I like the sheep skin idea and always make sure the belt is not to tight or uncomfortable. Like one person mentioned, I need to pick my battles. She can't help what she does, she's kind of like a child that don't know any better.

Velcro cover over it (sheepskin padding that just
happens" to cover the belt release?)
can you figure out WHY she is trying to bolt? Seat belt uncomfortable? thinks she is trying to "escape" from prison?
maybe music she really likes on the CD/radio to keep her distracted
(back seat is a good idea -- lock the door "in case of accidents" or "to keep from getting car-jacked"), slippery lock switches?
Look up the child-lock in the car's manual (avail online). They have been around since the 70's, so it may have those locks, just not obvious (could be a switch in the door, door jamb, etc.)

thank you and that was cute, lol

Hi, campbelllee, hmmmm, I know there is a product on TV for kids mostly called a seat belt pillow or something. It wraps around the seat belt and makes a nice pillow for their head and softens the strap. Maybe it would help her keep the belt on if you make it more comfortable.
If she won't wear a seat belt I would make her wear a helmet and a life vest in the car! See if she likes that any better. Tell her it is the seat belt or the life vest -as big as you can find--- and helmet. Sorta kidding sorta not.
Good luck!

She is a elderly friend I take care of. I was concerned about seat belt laws incase I was to get stopped. She does have dementia and I understand her medical condition. The car is not equipped with what you mentioned and I don't believe the family wants to spend any kind of money worrying about. I guess I wont worry about it either and I know I'm a safe driver especially where she is concerned. I just can't afford to pay for the ticket and I hope the officer will take that into consideration on her behalf. Thanks for the advice as always.

Is this person your parent? Do he/she have dementia? If he/she has dementia it might be unreasonable to expect him/her to be reasonable and leave the seatbelt on in which case you'll have to find a way to work this out. Using child-proof locks is a good idea. I know my Jeep ('06) has a master switch on the console to keep the doors locked even if someone tries to unlock them. If your car has this feature you'll probably have to use it. As for the unbuckling of the seatbelt you might just have to let it go so you won't drive yourself crazy over it. If this person absolutely will not use a seatbelt let them be. Pick your battles. Opening up the car door while the car is in motion is a battle you want to wage. Trying to convince someone to use a seatbelt may not be worth your energy.