private void radSelUser_CheckedChanged( object sender, EventArgs e )
{
lstUsers.Enabled = radSelUserFromList.Checked;
lstUsers.SelectedItem = null;
txtUserID.Enabled = radSelUserByID.Checked;
txtUserUrl.Enabled = radSelUserByURL.Checked;
if( radSelUserFromList.Checked ) {
SelectUserInList( txtUserID.Text );
}
}