Using the value in a ComboBox as the url for a Fram

I have 2 small problems (rather newbie questions actually, since I’m pretty new regarding web applications) that I could need some guidance to solve:

I need to design a portlet where I can view the content of a list of URLs (one at a time of course).
To use this I’m thinking of using a Frame Control to display the select URL, a ComboBox to select the page to show and a button to refresh the frame.
Since the URL list will be appended by the user with time (imagine a Favorites list), so I’ll need to persist the URLs for future sessions.

Problem 1:
How do I persist the URLs? Can I really use a combobox for both inserting new lines and selecting the one I want?
I know I need to put a combobox inside a form control, is there any other control that I need?

Problem 2:
How do I use the selected element in the combo to feed the Frame?
I know the value property should be used, but how do I change it dinamically?