I gotta go with Kathryn on this one. If your text box is bound, all you will be doing by entering search criteria in the text box is changing the value of the field it is bound to in the table.
If you want to have a searchable form, have an UNBOUND text box for your criteria. Then after update of the field you can:
1) Create a dynamic SQL string based on your criteria,
2) Set your forms Record Source to that string, and
3) Refresh your form.
This is just one way that I like to use, I am sure others may have some methods they prefer. If you need help with the SQL statement, let us know.