When you save the document, this property specifies whether the library path should be saved as absolute or relative. When true, the path of the library will be relative to the document. When false, the library path will be absolute.
Do not rely on this property to determine whether the path is absolute or relative, since the path may have been changed (either from the user interface or via API) since the document was loaded from the .mfd file.
If you set this property (either via API or via user interface), the "Manage Libraries" window does immediately show the correct path’s state in the user interface. Internally, however, the Path of the ImportedLibrary object will not be changed until the document is saved.
Libraries imported globally cannot be saved with a relative path. Only libraries imported at document level can.
SaveRelativePath : Boolean
The object is no longer valid.
Invalid address for the return parameter was specified.
Global imports cannot be saved with a relative path.