Populating one cell or another in pair of data validation driven drop down columns.

Dear All,

Nearly finished my latest project which is a kind of money tracker for my 75 year old mum, and run into one final issue which I can’t get my head around!!!

Basically, all the calculations work, but I’ve tried to make it near on bullet proof as my mum is not very IT saive.

In a nutshell.....

The issue is with two columns (e and f), which are driven by a selection from d14, d15 etc.

Once a selection is made in column d then either column e or column f are populated with a request that the user selects from and that value populated via the corresponding drop downs.

I’ve used both data validation and worksheet change code BUT once the driver column is selected, then user can simply go back to either column e or f and select another item after completing the above, therefore it is possible to have BOTH columns (e AND f) populated, which is what I want to be impossible. See example file for demonstration.

The calculation is still valid but my mum will still simply see two inputs in columns e and f which is what I’m trying to prevent as this column should be wholly depended on column d and as I’ve said beforehand I really would like this to be as bulletproof as possible.

Hope you guys can help as hopefully this little worksheet will see her sort out her finances at long last!!

Thanks for looking

Skyping