Need To Convert Google Search Ref To Find What The User Search

i get the ref url that come to my site and i want to convert it to find
out what was the query in (google or other searcher sites)

foe example : if someone goes to google and search some text and my
site was in his resaults and he click on it , in my site i see his link
ref like
http://www.google.co.il/search?hl=i...91-Google&meta=

i want to know (in asp and save it to DB) what was the word or words
that the user write in search engine.