If an executor of a will does not follow the instructions, what can I do?

All of the possessions were to be divided between my 3 younger brothers and myself, Instead, my younger brother who is the executor (I live out of state) is telling me to pick out a few "mementos" and the rest is going to be put into an estate sale; if anyone wants anything they'll have to BUY it after it's appraised by the auctioneer. THIS IS NOT WHAT MY MOM WANTED!! She was the president of the town's historical society for 20 years. There are antiques she has kept for generations. She must be TURNING OVER IN HER GRAVE to think these cherished family items will be turned over to a stranger. HELP!