Disabling Text on Radio Click [resolved]

[mrstuff68]

I have several radio buttons on my site with the following tags.

<INPUT TYPE="radio" NAME="index_Radio" VALUE="Radio A" SELECTED>
<INPUT TYPE="radio" NAME="index_Radio" VALUE="Radio B">
<INPUT TYPE="radio" NAME="index_Radio" VALUE="Radio C">

Then I have and input field with the following tag.

<div id="first_name">
First Name:&nbsp; 
</div>
<INPUT TYPE="text" NAME="first_name" SIZE="20" MAXLENGTH="10" ONCHANGE="this.value = this.value.toUpperCase()">

What do i need to do to have the First Name label and the text box disabled when I click on Radio A. And have it enabled when i click on B or C. Keep in mind that when the page loads A is selected already. So it needs to load disabled.

Thanks for you help