To set a combobox, you can either set the selectedindex value of it to the desired index you want, or you can set the value to whatever value you want

Obviously either the selectedindex or the value has to be a valid one (ie you can't specify a value that doesn't exist in the list)

Also remember that a value is NOT the same thing as what is displayed in a combobox.

Combobox HTML code looks like
Code:
<select id=cmboSelect>
<option value=""></option>
<option value="a">Apples</option>
<option value="o">Oranges</option>
</select>
so if you wanted to set Apples you would need to set the value of the combo to "a"