update drop down as soon as hitting add button on another form

[redshirtme]

here is the scenario:
I have drop down box on webform1.aspx and a link to bring up webform2.
on webform2, there is "add" button and text box which could add a new entry , how can I after click add button on webform2, the drop down list on webform1 gets updated as well.

so user doesn't need to hit refresh to see the changes