A---<B>----C. This makes B a typical "Join" table.
There are several options. How do you determine that it will be the second record? If you have a button in a portal to B on the A layout, Go to related records can bring up this record on a Table C based layout. It may, in some cases take to GTRR steps, one to isolate the correct B record on a B based layout followed by a second to isolate the C record, but I would only try this if a single GTRR to C fails to work for you.
You can also establish different relationships using a different occurrence of C linked to a different match field in A. You use Go To Nth Record to access the Primary key value of the related C record and set this additional match field to that value to link the current record in A to the desired record in C via this added Tutorial: What are Table Occurrences?.
Thank you for the response, very helpful. The information isn't being accessed through a portal, it's a script that fires dependent on the field in the "C" table. Your second solution will work in this situation though. Thank you, I just needed a set of outside eyes as I couldn't see the wood for the trees. Thanks again for your help :)