@sj365 - Apologies for the delay in following up, and welcome to the Seller Community!

As for your question, since the tracking number is only sent to the customer when the order is marked as completed, there isn't a way to update it after that point. I'd suggest using the contact information collected during the order to reach out separately to the customer with an update. Hope this helps! 

PS) If my answer solved your problem, would you mind marking it as "Best Answer"? That'll help the rest of the community find what they're looking for. If not, just write back, and I'll continue to help. Thanks!