Application.Caller return value

[SamT]

The UserForm should have a Public Variable. ie Public "CalledBy" As String
You will need an intermediary sub to determine the caller and to call the calendar.
The buttons should call the intermediary sub

Sub Intermediary()
   Load UserFormCalendar
   UserFormCalendar.CalledBy = Application.Caller
   UserFormCalendar.Show
End Sub

Edit terminology to suit