Calculating an average for missing data over a variable range (without using macros!)

I'm creating a monthly petroleum production report to be used by my company's well pumpers. Each day of the month needs a row, but because of our pumpers' schedules they cannot obtain readings every day of the month. For days without readings, the next recorded readings are averaged over the days for which the data is missing.

I am trying to write a formula for the calculation of the "production" column that calculates an average over a variable range WITHOUT using macros. (Is this even possible?) I am insisting on no macros because of the wide number of machines and excel versions that will be using this spreadsheet.

I've attached an extremely simplified production report that should clarify my problem:
Production Example.xlsx

Thanks so much for any help that can be provided!

I should clarify that I am trying to have column D calculate automatically based off of the data from columns B and C. For the example that I originlally attached, I calculated all of that data myself. -- THANKS!