Originally posted by hesham katon: but when i try the third one i cant make it work
What problems are you runing into. Just telling us that it doesn't work doesn't give us any information on how to help you. The same principles you applied to making the 2nd select element (it's not a "combo box") work should alos work when applied to the 3rd.
Given no other info, I'd suspect that you are running into a problem using global variables.