Husband swearing to divorce his wife if she sees his sister at her house. Is this divorce effective if his sister comes to his house?

Q: My wife and I paid a visit to my sister in her house. When I wanted to return home, my wife refused saying, "Let me stay for the night at your sister's house or take me to my family's house." An argument ensued between us. I gave my wife conditional divorce saying, "You will never come to my sister's house nor see her except in the house of my other sister." She will be divorced once if she does so. Is this divorce effective if my sister comes to my house? I want to maintain family ties (Part No. 20; Page No. 114) seeking the reward from Allah. It is noteworthy that I gave no divorce except this one, and my wife did not go to my sister's house since the divorce was pronounced in Dhul-Qa`dah, 1393 A.H.

A: If the reality is as you mentioned that you issued conditional divorce by making one pronouncement if your wife goes to your sister's house where she wanted to spend the night or sees her except in the house of the other sister, the divorce will not be effective in the following cases: When the other sister or your sister in whose house the argument occurred comes to your house, and when your wife sees either of the two sisters in your house or in the house of the sister in whose house the argument did not take place. However, the divorce will be effective, if your wife visits your sister in whose house the argument took place. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.