I have a ticket like this:

A connecting in B, to C
C connecting in B, to D
D back to A.

Instead of "C", I want my first destination to be X. So what I want is:

A connecting in B, to X
X connecting in B, to D
D back to A.

The thing is, I can get a ticket B-X-B for less than the change fee on the original ticket. Can I fly A-B, get off the flight, and on my new ticket, fly B-X-B, and then get "back on" my original ticket?

My guess is "no", but I wonder if there's any way to do this?

I don't even so much mind paying the change fee, but the airline wants to reprice the entire itinerary which would cause the price to jump thousands of dollars. I'm even willing to fly just A-B, B-D, D-A (leaving out C and X entirely) and that too costs thousands more.

Is there any way I can work something out that lets me make the change for several hundred, as opposed to several thousand, dollars?