This example opens or activates the data source attached to the document named "Sales.doc."
Documents("Sales.doc").MailMerge.EditDataSource
This example opens or activates the attached data source if the data source is a Word document.
Set myDataSource = ActiveDocument.MailMerge.DataSource
If myDataSource.Type = wdMergeInfoFromWord Then
ActiveDocument.MailMerge.EditDataSource
End If