Web Forms :: Onselected Index Change Not Firing

I can't get my OnselectedIndexChanged to fire. 

<asp:RadioButtonList ID="Pending" runat="server" AutoPostBack="True"
OnSelectedIndexChanged="Populategrid" Height="16px"
RepeatDirection="Horizontal" Width="755px">
<asp:ListItem Value="250">Pending Over 250</asp:ListItem>
<asp:ListItem Value="300">Pending Over 300</asp:ListItem>
<asp:ListItem Value="350">Pending Over 350</asp:ListItem>
<asp:ListItem Value="400">Pending Over 400</asp:ListItem>
</asp:RadioButtonList>
 
[code]....

Since I am staying on the same page do I need something in pageload?I put this in pageload but it doesn't do anything:

If Page.IsPostBack = True Then GridView1.DataBind() End If
 
I do have this in pageload too could this be messing it up? 'used for a back button on the page. So when use sort several times you can click on the button to go back to the counts.

If Page.IsPostBack = False Then
ViewState.Add("NbrPostbacks", "1") Else
ViewState.Item("NbrPostbacks") += 1 End If
btnback.PostBackUrl = String.Format("javascript:history.go(-{0});", ViewState.Item("NbrPostbacks"))