Exact Search Results
It can be done navigating to Administer -> Customize Data and Screens -> Search Preferences, the first option is Automatic Wildcards, disable it.


  If enabled, wildcards are automatically added to the beginning AND end of the search term when users search for contacts by Name. EXAMPLE: Searching for 'ada' will return any contact whose name includes those letters - e.g. 'Adams, Janet', 'Nadal, Jorge', etc. If disabled, a wildcard is added to the end of the search term only. EXAMPLE: Searching for 'ada' will return any contact whose last name begins with those letters - e.g. 'Adams, Janet' but NOT 'Nadal, Jorge'. Disabling this feature will speed up search significantly for larger databases, but users must manually enter wildcards ('%' or '_') to the beginning of the search term if they want to find all records which contain those letters. EXAMPLE: '%ada' will return 'Nadal, Jorge'.


Please note: forgot to mention that changing this option will change the behaviour for all contact search forms, not sure if that's what you want to achieve, if it's not, @petednz comment is a very good and better answer