Mel B's making it incredibly difficult for Stephen Belafonte to sell one of their houses because she won't let him in the house ... this according to Stephen Belafonte.
Stephen filed new docs saying Mel's breaking a divorce deal they hashed out back in November that included allowing Stephen into one of their houses so he can make repairs, stage it and help unload it.
In docs, obtained by TMZ, Stephen says he's been in contact with a realtor who has a buyer with plenty of cash and is interested in buying the crib. Problem is ... Stephen claims Mel's blocking his efforts. He said the potential buyer has more than $6 million in cash in one bank account and even offered to swap houses if that would make it easier for Mel.
Stephen also says Mel's not letting him see their kid. Stephen's case in point -- when he showed up to pick up 6-year-old Madison at school only to find out the nanny beat him to it.
Stephen wants the judge to enforce the deal they agreed to.