I attached a sheet of my oil change worksheet. In the Hours on oil column I would like it to automatically subract the miles from the previous time I selected "changed" in the Oil Column. Currently it just subtracts the current row from the row above. The problem is if I do other work on the piece of equipment, it still subtracts the the miles and figures it in the oil column. The only way I can get around it is to not put miles in the row, but I don't like doing it that way. Thanks for any help.