Sub Index Based on Condition from Previous/Next Rows in Power Query

I’m working with a dataset in Power BI and using Power Query to prepare my data for reporting. The dataset tracks multiple trips using the following columns:

• ShiftID: Represents the time when a truck starts its shift at the depot and returns to the depot.
• StopType: Either a stop at the Source (S) or Customer (C).
• StopOrder: Indicates the order of stops in a shift (resets for each new ShiftID).

I need to create a new column in Power Query called TripEvent that increments based on the following rules:

1. For each ShiftID, the trip event starts at 1, regardless of the first stop (whether it is a Source or a Customer).
2. The trip event remains the same as long as the truck is stopping at a Customer (StopType = 'C').
3. If the truck stops at a Source (StopType = 'S'), a new trip event begins, so the trip event number is incremented.
4. If the last event is a stop at a Source (StopType = 'S') and there are no further deliveries (Customer stops), the trip event remains the same as the previous one (i.e., no increment).

How can I achieve this conditional column logic in Power Query, where the TripEvent column increments and reset based on these conditions?

Thank you in advance for any assistance!