Merge command: [strcalendar-boxunid ]
Merge variable/item: strcalendarLinkUNID

Comments:
This contains the unid of the document (database or category) that was used as `source` of the calendar box.

Formula:
@If(strSourcetype="category";strcalendarLinkCategoryID;strSourcetype="database";strcalendarLinkDatabaseID;@Text(@DocumentUniqueID));