Hi
Certainly is:

Put this in the code module behind your sheet that the dropdown is on
(in Editor, double click the sheet name)

Private Sub Worksheet_Change(ByVal Target As Range)
If Not Intersect(Target, Columns("P")) Is Nothing Then
If Target.Value = "no" Then
Response = InputBox("Any Reason?")
Target.Offset(0, 1).Value = Response
End If
End If
End Sub

regards
Paul