WriteReservedBy Property
Returns the name of the user who currently has write permission for the workbook. Read-only String.
Example
If the active workbook is write-reserved, this example displays a message that contains the name of the user who saved the workbook as write-reserved.
With ActiveWorkbook
If .WriteReserved = True Then
MsgBox "Please contact " & .WriteReservedBy & Chr(13) & _
" if you need to insert data in this workbook."
End If
End With