I have the follwing booked:

EWR-ORD-HNL-ORDx-EWR (where x indicates a connection)

In other words, there is a stopover in ORD on the outbound and a stopover in HNL where we're going for vacation.

Can I legally buy another ticket ORD-DEN-ORD during my first stopover in ORD so that my itinerary looks like this? :

EWR-ORD-DEN-ORD-HNL-ORDx-EWR

Many thanks - I don't know if this would be considered illegal or not. I think it's end-on-end ticketing, which is OK, but just wanted to make sure. Thanks.