OOOHhh... OK, so the last bit of the constant, is that the page name? That makes sense. I was reading it more as a description of the event. So when we're talking about NOTIFY_HEADER_START_CHECKOUT_SUCCESS, is that saying "I'm notifying that the header for checkout_success has started"?

Perhaps not though, because what page would the one I chose relate to?

NOTIFY_CHECKOUT_PROCESS_HANDLE_AFFILIATES

I chose that one because I figured that any code relating to handling affiliates, which is normally determined on actual sales, that it would be least likely to be affected by reloads and such.

Thanks for help and suggestions folks.