New tab in admin in product page

[GiorgianaM]

Hello,
I want to add a new tab to admin product's page (near Info, Images, etc). In this new tab I want to upload pictures related to my product, similar to tab no 2 - Images.
First step was to modify the code below in AdminProducts.php, in method "displayForm"

$this->displayFormImages($obj, $languages, $defaultLanguage, $token);
if ($obj->id)
       echo '
3. '.$this->l('Combinations').'
4. '.$this->l('Features').'
5. '.$this->l('Customization').'
6. '.$this->l('Discounts').'';
$this->displayFormNewTab($obj, $languages, $defaultLanguage, $token);

Then I made a new class and the related tables.
In displayFormNewTab I have

global $cookie, $currentIndex, $attributeJs, $images;

echo '

7. '.$this->l('New Tab').'';

And this new tab appears.
From here I need your help, the code must be similar to the one from displayFormImages, but I don't manage with it.