|Publisher Developer Reference|
Version Added: Publisher 2007
expression A variable that represents a MailMergeDataField object.
The parent MailMergeDataField object must represent a field (column) in a connected data source that is not the master data source (the combination of all connected data sources). The IsMapped property is not available for data fields in the data source represented by the DataSource property of the MailMerge object of the active Document object (