Hi Oskar,
I'm not sure it the interface of Annotation setting support the access via VBA. There are also no documented Keyins for setting another Cell.
But if you have some basic Basic knowledge you can change the Cellname in the annotationoverrides.xml (in the Project Folder C:\ProgramData\Bentley\AECOsimBuildingDesigner V8i Ss6\WorkSpace\Projects\BuildingExamples\BuildingTemplate_UK\support\dataset\setting)
Then reload tfannotate and the new setting should be available. mdl unload tfannotate; mdl load tfannotate