Workbook.ConflictResolution (Excel)

Returns or sets the way conflicts are to be resolved whenever a shared workbook is updated.

Possible Values are xlLocalSessionChanges - The local user's changes are always accepted, xlOtherSessionChanges - The local user's changes are always rejected, xlUserResolution - A dialog box asks the user to resolve the conflict.
ActiveWorkbook.ConflictResolution = xlLocalSessionChanges