categories search

Hi, i actually want to ask how i can search multiple categories.

for a example i have 4 drop down menu
1.City
2.Area
3.Month
4.Products/Services
(This are my 4 categories in my wordpress)

so any user visit my site. a static page will open there will be 4 drop down list to select and a button name search, after selection all 4 the categories, the search will go selected categories by user in my wordpress

please se this image below made by me for better understanding
http://i49.tinypic.com/160x5ao.jpg