Data Validation

Hi Olivier, thanks for your query. A professional solution to this problem would almost certainly involve some code to capture cell changes and alter the properties of subsequent cells accordingly. However, you might be able to achieve a similar result by using conditional data validation and dependent drop downs. There is a good walkthrough of these at this link:

http://blog.contextures.com/archives/2010/10/11/excel-conditional-data-validation/

...and I would set up the dependent drop down boxes, thereby driving the user to pick from certain lists (I would create lists with 0 entries to pick from when a user was not meant to put anything into a cell) and then protect the whole worksheet, preventing ad hoc data entry. All this will involve a certain amount of work but it can be done.

Hope this helps,

Anthony