ListBox and SelectedindexChanged

I have two list boxes and I want to fill the second one based on the selections in the first one. the catch is the first one is a multiselect box. Will Selectedindexchange work in this instance, I am assuming that if the person makes two selections then this event will fire twice, is that true, is there a better way to do this.You'll need to iterate through the items selected in the first listbox, in order to get your results...

check out these:
Listbox - Selecting Multiple Items

and
3 DropDownLists Dynamically (yes, this is about DDLs, but the mechanism and syntax is the same - - you'll just need to build your select statement, based on the multiple results from the first list box)