Great Spreadsheet and very useful, the only suggestion I would have is as Harly says, make the depth +1,+2, -1, -2 and so on. That is how I have always understood the system, you start at 0 and if it is up one then it is +1, if it is down one from 0 is it -1, if it is up 3 then it is +3 and so on ^^