Excel Formula Question - Logic cycle

Hello all,

So I'm brand new to this forum and I'm having some excel troubles.

I'm creating a spreadsheet which cycles through equipment. Each equipment set is lettered A,B,C,...ect and each set has its own "travel distance". My overall goal is to balance the equipment across a 3 day cycle. So each equipment and its distance represents one day of travel. The spreadsheet is setup so it goes:
Column A is the equipment letter starting that day (A B C D...ect...,
Then column B is the equipment's travel distance (miles)
Then column C is what the equipment letter set will turn into the next day. (A B C D...ect...)

My goal is to have excel logically figure out when the 3 day cycle has cycled back to its original equipment set and to sum the total distance traveled for that 3 day cycle So for example:

If Equipment A (on day 1) turns into Equipment B (on day 2) then Equipment C (day 3) and then back to Equipment A on the following day...how long has this equipment traveled during that cycle.

I have tried for quite some time using IF functions however I seem to be missing some key detail. And and all advice will be greatly appreciated, I'm at quite a loss.

Doc