Add coments VBA

Hi,
I am trying to make a macro that insert automaticlly a comment if a cell match a certain condition. If there is a cell with the value "o" it should appear a comment box.
So far I got this:

Sub EjemploComentario()

Dim rg As range
Dim addcoment

rg = Sheets("Leavetracker").range("B8:NH27")

For Each cell In rg

If cell = "o" Then
ActiveCell.Select.addcoment

End If

Next cell

End Sub

Can you help me ?

thanks