AUTOCOMPLETE FIELD USING WEBSERVICES

Hi all,
i would like to try to prebuild the select list of an autocomplete text field, using my webservices request, that retrieves data from an external DB.
i’m able to make the WS request using PHP in drupal.. and i’m able to put the WS result into an array..
could you help me with the rest? Which field type i have to select? i’ve to wrte a custom module for prebuild de select list? what hook function i have to use?

thanks all for your support..

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