iOS build - Pointing to the right Xcode

I have Xcode 6 beta and previous versions of Xcode installed. It seems, Unity iOS build defaults to the highest version number.

Is there a way to have Unity open the right version of Xcode for iOS build?

If XCode 5 is already running when you build&run the Unity project, Unity will launch your project in that version.

The system is the one that decides which XCode app will be opened.