PRODUCTSUM of Each Duration for Each Category

My problem is this: I want to record each duration of time there is an "oil change" for each Bus. See attached example. For the 1st oil duration, it should sum up certain values in column B if oil change is "Yes" until next oil change occurs in F3. So every time there is an oil change ("yes"), it will start a different sum until another "yes" oil change occurs. The sums will be displayed consecutively in rows starting from F3 and moving to the right; G3, H3, and so on. Data will constantly be added to columns B and C in order with respect of their date. Also this would depend on if it is Bus no. 1 or 2. i.e. Sum the first oil change duration for Bus number 1 and display this data in F3 while Bus number 2 sum is in F4.

In short I need a SumProduct function to sum hours drove for each oil change based on criteria:

• Duration of oil change ("Yes" is start of a new oil change)
• Bus number