I have a field that could have the next values: Y or N.

In my program, I have a search form, where the user can search on
this field. But it is not nice to let the user press the Y or N.
After the user press one key, the form execute direct the query. So
after every key input, the search results are refreshed.

So I want the possibility to let the user input YES or NO.

Maybe it is now more clear.