Not possible - there's no preference option to turn this off.
Instead of preformatting as text, entries can be made with an
apostrophe as a prefix:
'3/4
You might be able to use an event macro to change it back
retroactively, but that depends on knowing what format the user
entered it. For instance,
3/4, 3-4, 4Mar, mar4, etc
will all be interpreted as 4 March 2003 (with US settings), or
serial number 36222. Unfortunately, by the time VBA has access to
the data, there's no clue as to which one was originally entered.
Post back if that's an option.
Depending on your application, another alternative might be to use a
userform for entering data, parsing it in code and putting the
result in the cell.
If there are specific combinations that you use (like 3/4), you can
use an event macro to enter an autocorrect (Tools/Autocorrect) that,
for instance, changes 3/4 to '3/4. You'd want to take them out in
the Workbook_Deactivate event, though, since Autocorrects apply
across the Office suite (e.g., in Word) as well.
