How can i build a Drop Menu on Search Bar ?

[Searchtheweb]

Hi,

I use arfooo script on a classifieds website, i think in french it is annonces. I want to have a drop menu on the search bar with a tree formed by each category and afterwards its annonces and so on.

This is an example:

- Annonces gratuites
-- Annonces gratuites achetes
-- Annonces gratuites Animaux
- Annonces auto
-- Je vends
-- J'achete

Mercy beacoup. J'ai besoin de le code!