Untitled

Sub SummarizeColumns()
    Dim lastRow As Long
    lastRow = ActiveSheet.Cells(Rows.Count, "Q").End(xlUp).Row
    Dim col As Long
    Dim startingCol As Long
    startingCol = 17 'Q column
    For i = 4 To lastRow
        If Cells(1, startingCol).Value = "VO" Then
            For col = startingCol To ActiveSheet.Cells(1, Columns.Count).End(xlToLeft).Column
                If Cells(1, col).Value = "VO" Then
                    Cells(i, "G").Value = Cells(i, "G").Value + Cells(i, col).Value
                End If
            Next col
        Else
            Cells(i, "G").Value = Cells(i, "S").Value
        End If
    Next i
End Sub