Can I change the venue of a post-decree case from County A. . . to County B? (Child custody modification on the horizon.)

I'm a father in Illinois. Mother is the custodial parent. JPA exists. But she does not abide by it. Mediation was unsuccessful. And there is now significant potential for this to go into litigation. Case started in County A, where the Divorce occurred. Mother moved to County B. I did not. Post-decree case is expected to be in County A (even though the mother no longer lives there.) County B (where custodial parent mother lives) is subjectively considered more favorable to fathers in general. Under what circumstances can a change of venue be requested? I want to move it to County B, where