I have a spreadsheet which has a large number of rows. Each row has 3 columns (B,C,D) that can contain numerical data that has been collected at three different points in time. B = first time point, C = second time point, D = third time point. When it was not possible to collect data at a given time point, the cell contains a zero.

For each row, I would like to

- Create a 'Total Column (column E) for each row.
- Enter 'no result' in the total column (column E)for any row in which only contains one number (irrespective of whether this is in column B, C or D)
- Subtract the number in the latest data collection time point that contains a number from the number in earliest data collection time point column that contains a number

Can anyone help?