Help with this Search button

Hi

I have a database of students.

I have created a search box (through an unbound box).

I have the following in the rowsource:

Row Source: SELECT DISTINCT [First Name] FROM T_Participants ORDER BY [First
Name];
Row Source Type: Table/Query
Bound Column: 1
Lmit to List: Yes
Allow Value List Edit: No
Inherit Value List: Yes
Show Only Row Source: No

While a list of names does appear in the search box, the form below the
search button does not change.

What do I do to fix this button so that it gives me the desired form?

Thank you in advance for your help.