House hasn't sold/modify agreement

My husband was separated in June 2006. At that time, his ex-wife didn’t work and therefore his separation agreement stated he must pay the mortgage until the house sold and that his ex-wife would pay all costs associated with “occupancy” (such as utilities, taxes, upkeep, etc.) The INTENT of this agreement was so that my husbands minor son, at that time, would be able to stay in the home. Well, the ex-wife moved out of the house in November 2006 and moved in with her boyfriend and then remarried the day after the divorce was final in Aug 2007. The house has been for sale since Jun 2006 and my husband continues to pay the mortgage and ALL upkeep on the property - we drive 3 hours one way twice a month to mow the lawn because she refuses to do it (she lives 10 miles away) because she says she doesn’t “occupy” the house anymore - she has never paid a dime on the house - nothing! We are just about to go under paying 2 mortgages and the economy holds no hope that the house is ever going to sell. Are there any options to modifying the divoce agreement?? We have lost tens of thousands of dollars on the house that will never be reouped. Can he auction the house off without his ex agreeing? the “Agreement” states they must agree on a realtor, but mentions nothing of any other selling options. Please help.

Unfortunately Separation Agreements are not modifiable, and unless the ex wife agrees, the home cannot be auctioned.