Get related items on form load event

Hello, im trying to get the related items of an item on its form load event. The code im using looks like this :

var item = document.thisItem; var related_items = aras.getRelationships(item.node, "MY_RELATIONSHIP");

but if the Relationship grid hasnt been loaded before the related_items is empty, is there a way to force load the Relationship grid before trying to retrieve the related items? Thank you. Léo