Well I want that user can select an item to have access level public or special depending on extrafield value.....that he adds from frontend.

 

I have an extrafield with dropdown box yes/no...if yes then item should be not public.....

 

so for that i need to check the value of extrafield while saving. What code will be executed when click on save button so that there i can check the value of the extrafield and then change the access value to 1/2 from 0......