brakes squeal in reverse only

My 2003 windstar squeals LOUDLY when in reverse. The brake light comes on also. After I put it in Drive, the light goes out. The brakes NEVER squeal while going forward. I have taken it to the dealership 3 times and they always tell me it's normal. It can NOT be normal. People always comment on how loud the brakes are.
Any ideas??
I am a single mom and haven't the slightest Idea about cars so any help would be appreciated!!

daisymom, welcome to the forum.

Is the brake fluid at the proper level? Should be near the MAX line. The master cylinder reservoir is lined up with the steering wheel under the cowl. Normally cream colored plastic tank.

Squealing could be worn pads...the indicator clip is hitting the rotor. How many miles on these disk brake pads? Are they original?

If you've taken this problem to the dealer 3 times and it still squeals, I'd find another dealer for a 2nd opinion (If under warranty). If not under warranty - a good brake shop.