Deleting a .NET Membership User from Gridview

Hello,
        Following the steps described in the Security Tutorials (http://www.asp.net/learn/security/) I'm trying to implement the ability to delete a user.  I'm trying to integrate the ManageUsers.aspx and RoleBasedAuthorization.aspx pages.
        Using ManageUsers.aspx page as a guide, I've added a Delete link button (for a confirm prior to delete).  But when the event fires, I get a "Index was out of range. Must be non-negative and less than the size of the collection.  Parameter name: index" error.  This occurs at line 3 of the VB behind code.

        How would I got about resolving this issue?  Thanks.. -Jeff

1    <asp:GridView ID="UserAccounts" runat="server& ...