Marynella,
Once you add a checkbox, you can use the Show() and Hide() methods to... well, hide and show it. Here is some sample code to demonstrate:

use strict;
use Win32::GUI;

my $Window = new Win32::GUI::Window(
    -name   => "Window",
    -left   => 100,
    -top    => 100,
    -width  => 150,
    -height => 150,
    -title  => "checkbox test",
);

$Window->AddCheckbox(
    -name    => 'mycheckbox',
    -left    => 10,
    -top    => 10,
    -height    => 15,
    -width    => 15,
);

$Window->AddButton(
    -text    => 'Hide checkbox',
    -left    => 10,
    -top    => 35,
    -height    => 30,
    -width    => 100,
    -name    => 'btnHide',
);

$Window->AddButton(
    -text    => 'Show checkbox',
    -left    => 10,
    -top    => 75,
    -height    => 30,
    -width    => 100,
    -name    => 'btnShow',
);

$Window->Show();
Win32::GUI::Dialog();

sub Window_Terminate {
    return -1;
}

sub btnShow_Click {
    $Window->mycheckbox->Show();
}
sub btnHide_Click {
    $Window->mycheckbox->Hide();
}
[download]

Update:
If you really want to *remove* a checkbox or combobox, something like this might work:

Win32::GUI::DestroyWindow($Window->{mycheckbox}{-handle}); 
delete $Window->{mycheckbox};  #use hashref syntax instead of autoload
+ed methods
[download]