Event handling

Question

I have to fill a list box with some values.. Select a value. As soon as i select i should get another dropdown list containing values related to the selected value. And after i select a value from the second dropdown i have to display something on the same page related to the second value selected. I am getting the first dropdown.selectedindexchanged event handled properly. But the second dropdown event handler is not getting called. I have put the loading of first dropdown in page_load event and given a separate event handler for each dropdown. In first handler i get the selected value and display the second dropdown. In the same event if i lauch the second event handler it goes back and loads the page again with only the first dropdown. Give me some solution.

Putting these things in Page_load is wrong?