Dropdownlist: Selected value populated using querystring

Hello (I'm using VB),
I'm having an issue trying to get the selected value in a dropdownlist to be a querystring passed to the page.  My code is as follows:
 
<asp:DropDownList ID="AList" runat="server" AppendDataBoundItems="True" AutoPostBack="True" DataSourceID="ADDLDS" DataTextField="ATitle" DataValueField="AID"> <asp:ListItem Value="">-- All --</asp:ListItem> </asp:DropDownList>
 
 So I have the element "--All--" as a listitem + the databound elements.  I want to have the SelectedValue="Querystring".  I also want to remove that querystring element from the databound list that shows up in the dropdownlist at the same time (this second part isn't as important to me; so will only do it if it ...