Is there an existing hook that would allow me to replace the items in appointments

I have a custom piece of code that calculates my clients business accounting for all the variables, distance, gasoline, traffic, travel time, hotel etc... I just need to be able to make the appointments plugin easily use MY quote number instead of the existing services, because the calculation is relatively complex conditionally...

So without having to manually input the quote data, it could be generated by selections the end user makes and then calculates a figure... (All of which is done on my end already) then feeds into the hook in the Appointments+ software that allows some condition (if isset - maybe) to make my input variable the input quote figure and then carry on with the rest of the quote, billing auth, and booking? yes?