Notice on login page when account created – plugin?

I need to be able to run some custom javascript when a user creates an account.

I’ve looked to write a plugin that sits around the

MagentoCustomerControllerAccountCreatePost

event and can see, with xDebug, the afterExecute function in my plugin firing.

I need to be able to notify the account page (where the user is returned to once the account has been created) that the previous user step was account creation.

I’ve spent a few hours trying to work out how to do this. Any ideas, pointers?

Whatever method needs to be able to be read/seen by JS on the account page.

Thanks