disable radiobutton listitem

I have 2 radio button list  each containing 2 radio buttons each...so I would like to disable radion button present in 2nd radiobutton list based on value in first list. How can I achevie this.
<div> Which Type of Contractor will be added? <div class="spacer"></div> <asp:RadioButtonList runat="server" ID="rblContractorType"> <asp:ListItem Text="ContrEmployee" Value="C" Selected="True" /> <asp:ListItem Text="SelfEmployee" Value="A" /> </asp:RadioButtonList> </div> ...