How do I use PackageMaker to update an existing framework bundle?

I have developed a framework where I changed the library API. I changed the installed version letter to indicate the API change. However, the old versions are deleted by Installer.

How do I build a package that will leave the old API version beside the new library?

For example, MyFramework v1.0 implements version A of the interface and is installed at /Library/Frameworks/MyFramework/Versions/A. v2.0 implements v开发者_如何学编程ersion B of the interface. It is installed in /Library/Frameworks/MyFramework/Versions/B. The Installer applicaiton keeps deleting the directory /Library/Frameworks/MyFramework/A. I want to keep that directory so that i have:

/Library/Frameworks/MyFramework/A
/Library/Frameworks/MyFramework/B