I have a worksheet where the costumer types in data. The data is later
used for data validation as a list.

My big problem is, that data validation based on a list is not Case
sensetive. This means data can be added that is not exactly the same
case "Yes" <"yes", etc.

The applied data data is exported to another program, that is case
sensetive.

Using upper case is not an option. I need to control that the user only
types in exact valid data.

Any ideas?