newbie question: Change RadioButtonList1 based on RadioButtonList2

Question

hello. very new to asp/vb.net - do have experience with other
languages, so not a code newbie, just asp/vb.net newbie 

i'm making a web form and have 3 radiobuttonlists (each with 3 choices
in them, all are the same value). example:
 
<asp:RadioButtonList id="rbl1" runat="server" RepeatColumns="3"
RepeatDirection="Horizontal">
  <asp:ListItem Value="A">High</asp:ListItem>
  <asp:ListItem Value="B">Medium</asp:ListItem>
  <asp:ListItem Value="C">Low</asp:ListItem>
</asp:RadioButtonList>

what i'm trying to do is when a user selects, for example, A from rb1,
then change rbl2 or rb3 if A was previously selected in rbl2/rbl3.

if possible, i would appreciate help with the code behind to swap the
value selected between 2 radiobuttonlists. and also if two
radiobuttonlist values are the same, then change the radiobuttonlist
not selected last to nothing.
tried various things in the code behind and the 2nd/3rd one was not
changing.
appreciate any help. thanks...