# Set up frames to contain all the pids (for selection) 
my $frame_pids;
$frame_pids = $main->Frame(-borderwidth => 2, -relief => 'groove'); 
   
my @sortedKeys = ( sort keys %IdxToNickName );
for my $k (@sortedKeys) {
   my $pid_nickname = $IdxToNickName{$k};
      
   my $cb = $frame_pids->Checkbutton( 
      -text     => sprintf("%-15s",$pid_nickname), 
                   # courier and -15 implies fixed length left justified
      -variable => \$IdxToNickNameSel{$k},
                   # this is a hash for the selection result (so others can access)
      -font     => ['courier', 10, 'bold'] 
                   #       and a font size   
      );
     
   $IdxToNickNameSel{$k} = 0;        # Initialise the selection to 0
      
   $cb->pack(-side => 'top');        # Pack the cb according to left criteria	
}