how 2 work with combo box using axWebBrowser1 ?

Question

for example in this site :
http://www.google.com/advanced_search?hl=en

how i can choose an option in any of the multiline combo boxes?
like Language, File Format.....
i mean for example in Language i wanna select some language
and in file format i wanna select pdf

i know how to enter data into textbox and click on botton...
like this

HTMLInputElement otxtSearchBox = (HTMLInputElement) myDoc.all.item("q", 0);

otxtSearchBox.value = "intel corp";

HTMLInputElement btnSearch = (HTMLInputElement) myDoc.all.item("btnI", 0);

btnSearch.click();

BUT.... i could not do it with combobox ....

does any 1 know how i can do it?

thx in advance....