I am having trouble with Excel not letting me change text that is in a
function. Try this to reproduce the issue.

1. Open a blank workbook
2. Type this into a cell =TEST and hit enter
3. You should now see #NAME? in that cell
4. Go back into the cell and change the formula to =test and hit enter
5. Go back into the cell and you will see that the formula has changed back
to =TEST

Essentially any text string entered will remain with its case in memory so
if you make a mistake, good luck changing it. I've confirmed this behavior
with a colleague who knows Ecxel pretty well and he has never noticed this
before.

Is it a bug or a feature? If it is a feature, how do I turn it off?