Find Max within range and add $15

Try something like this...

Sub FindMaxAndAddToIt()
Const fee As Long = 15     '$15 will be added to the max amount in col. N
Dim MaxTF As Double
Dim r As Long, lr As Long
Dim tfRng As Range
lr = Cells(Rows.Count, "I").End(xlUp).Row
Set tfRng = Range("N1:N" & lr)

MaxTF = Application.Max(tfRng)
If MaxTF <> 0 Then
   r = Application.Match(MaxTF, tfRng, 0)
   Cells(r, "N") = Cells(r, "N") + fee
   With Cells(r, "N")
      .Interior.Color = rgbYellow
      .Font.Bold = True
   End With
End If
End Sub

You're welcome. Glad I could help.
Thanks for the feedback.