Finally i have found the solution : I modified the trigger to the action of opening the custom options tab.
And here is my code in the observer :
$product = $observer->getProduct();
$option_data = array(
'is_delete' => 0,
'is_require' => true,
'previous_group' => '',
'title' => 'Height',
'type' => 'field',
'price_type' => 'fixed',
'price' => '0',
'sort_order' => 1
);
$product->setHasOptions(1);
$option = Mage::getModel('catalog/product_option')->setProductId($product->getId())->setStoreId($product->getStoreId())->addData($option_data);
$option->save();
$product->addOption($option);
Hope it will help someone sooner or later.
See ya.