Faster Way to Substract 2 Columns?

Range("M2").Select
    Range(Selection, Selection.End(xlDown)).Select
    
    Dim CEL As Range
     
    For Each CEL In Selection
    If CEL.Value <> "" Then
        If Range("O" & CEL.Row).Value <> "" Then
        CEL.Value = CEL.Value - Range("O" & CEL.Row).Value
        End If
    End If
    Next CEL
    
    MsgBox ("Done")

Is there a faster, better way?