I have a multi-city (A to B to C back to A) ticket booked some time ago and may need to only fly A to B and want to cancel the B to C and C back to A segments and retain the value for future use (minus the change fee of course). Is there any way for me to figure out in advance how much value will be retained if I fly A to B and then cancel the remaining segments? I called United once and the agent was very helpful but said she couldn't determine the amount. Is this something that can be done using the Fare Information feature on Expertflyer?

If this is already covered in an existing thread, would be grateful if you could point me to it as I didn't find it during my search.

Thanks in advance!