:sl: sis,
As an example, Ibn Taimiya (rahimahullah) states that a woman may put a condition that the man does not marry another woman. If he then does marry another woman, the previous wife would have the right to divorce if she so chooses. If, on the other hand, she has changed her mind about the matter and is willing to accept his violation of the stpiulation, that is also her right to do that.
From: The Fiqh of Family, Marriage and Divorce, by Jamal zarabozo, published by The American open University 1997
See also:
http://www.islamqa.com/en/ref/108806...age%20contract
:sl: