plugin events

Hi, I'm studying your code, I found that you entered only two events. But, is it possible add other events (i can change your code, but I'd rather not have problems with updates), for examples:
to add product:
file components\com_eshop\helpers\cart.php function add()
JPluginHelper::importPlugin('eshop');
$dispatcher = JEventDispatcher::getInstance();
$dispatcher->trigger('onAddProduct', array($key, $quantity));


Other question: you trigger event just from eshop folder, os it possible add other like system?
For example:
JPluginHelper::importPlugin('eshop');
$dispatcher = JEventDispatcher::getInstance();
$dispatcher->trigger('onAfterStoreOrder', array($orderRow));

to
JPluginHelper::importPlugin('eshop');
JPluginHelper::importPlugin('system');
$dispatcher = JEventDispatcher::getInstance();
$dispatcher->trigger('onAfterStoreOrder', array($orderRow));

thanks