how to deal with SelectedIndexChange of dropdownlist in Usercontrol Added dynamicaly

Question

hello everyone,
I have three DropDown list of Country,State,City in a User Control. I have populated the country DropDownList on page load of .ascx page ie. on UserControl. Now i want to populate the state ddl on selectedindexchange event of Countryddl bt finding difficulty to add that event on parent page.
plz can anyone help me to sortout this problem.