Place the following in the worksheet code  module:

Private Sub Worksheet_Change(ByVal Target As Range)
Application.EnableEvents = False

If Target.Count = 1 And Union(Target, Range("M:M")) _
.Address = Range("M:M").Address _
Then If Target.Value = "NA" Then Range("J" & Target _
.Row & ",K" & Target.Row & ",N" & Target.Row).Clear

Application.EnableEvents = True
End Sub


The block of 4 lines above is in reality one line with continuation
characters.