Theme/customize Field "city" from Location?

Hello Drupal-Friends,

It is possible to theme/customize every Location-Field alone in the Add-Form in Drupal 6? [city], [street], [postal code]?

I will add a jQuery-Autocomplete-Plugin to the city-field but i dont know how i can make this. The jQuery-Plugin is an input-id.

Has anyone an idea?

Sorry for my bad english.

Thank you and Regards
Matthias