How to call codeigniter function on change event of combobox using javascript?

[eluser]Rahul gamit[/eluser]
Hi,
I am having one dropdown box

Code:

<select id="opt_database_name" name="opt_database_name">
<option value="1">database name1 </option>
<option value=2>database name2</option>
</select>

so,whenever the user selects the database name from the combobox,based on the selected database name the list of available table list should be list.

so how can i call function of controller on "change " event of the combobox ??

Thanks in advance.