Untitled

Sub SummarizeColumns()
   Dim lastRow As Long
   lastRow = ActiveSheet.Cells(Rows.Count, "Q").End(xlUp).Row
   For i = 4 To lastRow
       If Cells(i, "Q").Value = "VO" Then
           Cells(i, "G").Value = Cells(i, "Q").Value + Cells(i, "S").Value
       Else
           Cells(i, "G").Value = Cells(i, "S").Value
       End If
   Next i
End Sub