PA,

You can't.

Your only option for that (and a much better way to go) is to create a form.
Put a textbox on the form.  Set the appropriat properties on the form to
limit the number of characters.  I would also put a button on your form that
will run/open your query.  Then change the criteria in your query to point
to the form instead of asking for input.  You would do that by changing your
parameter [prompt text that was entered] to [Forms]![FormName].[TextBoxName]
(I think that syntax is correct...I can never remember the placementes of
the !'s and .'s...this would need to be verified if you want to use this
method).  You don't need to put a button on the form to run the query but it
helps.  Although the form does need to be open when the query is run/opened.
You can program the button to hide the form so it is not in front of your
data,

Another option would be to put a list/combo box on your form and have its
source be a table/query of all possible values (or type in all possible
values into the appropriate properties).  Then it is just a matter of
selecting the option you want from the list and clicking the button to run
the query.

HTH,

Conan