usercontrol problem

Hello All,

I have to develop a usercontol which has a listbox. the listbox is populated on page_load, when the user selects a value from the listbox i have to display a dropdownbox with available options and when the user clicks the dropdownbox to select an option that option needs to be copied into a textbox. The problem comes with the dropdown box selectedindex changed event, when i select a value form the dropdown box the postback causes my listbox selection to disappear and the dropdown box is loaded again and i loose the selected value in dropdown box as well.

Here is my code so far, any suggestions will be greatly appreciated. Thanks in advance, Shilpa.
cs_data getdata = new cs_data();
prote ...