two combobox with ajax or javascript

[eluser]shahmy[/eluser]
Hi, I have 2 combobox in my view. that is 1.country, 2.Zone.
My problem is, when I select the country in a 1st combobox the proper zone should generate in a 2nd combobox dynamically. I was done it using php and ajax. But I don't know how to do these things in codeigniter. If any one know please help me.
Thank You.