customize "Only my items" field

[akkimca]

Hi,

i m wondering how to add some additional code in "Only my items" field in Basic Search form.
this img give u idea:

<input id="current_user_only_basic" type="checkbox" tabindex="" title="" value="1" name="current_user_only_basic"/>

i m getting this code by default so i want to add one function whenever this checkbox is changed link this:

<input class="checkbox" type="checkbox" onchange="this.form.submit();" tabindex="1" name="current_user_only_basic"/>

i debug the code but fail to find from where this code is generating

so pls help me to solve this issue

thanks in advanced