restarting a calculation based on a cell value

Hi -

I need to start a calculation at 70 and subtract a range of cells. If anywhere in that range = anything other than a number (can be a specific letter), I need to restart the calculation at 70 and subtract the remainder of the cells. Can anyone help me?

Thanks,
Beki

I am having a difficult time visualizing what you want. Can you upload a workbook with a couple of examples?