That's great thanks. Seems to be working so for.
This is my code:
func get_score():
var total_score = 0
var objects = get_tree().get_nodes_in_group("Objects")
for object in objects:
total_score += object.object_score
get_parent().get_node("HealthDisplay/HealthBar").value = total_score
edit: indenting now fixed. Thanks. It seems you use squiggles ~~~ instead of the 'code' option