On a search form, I've got two radio options. One "Search All" and another "Search Category".
After this, I have checkboxes of all the categories.

How do I get the radio options to change if one of the categories is chosen?

My form is like the following:

<form name=form1>
<input type="radio" name="SL" value="1"> All
<input type="radio" name="SL" value="2"> Categories
<input type="checkbox" name="ListID" value="1"> Cat 1
<input type="checkbox" name="ListID" value="2"> Cat 2
<input type="checkbox" name="ListID" value="3"> Cat 3

Any ideas?