Non-continuous Averages

[artiststevens]

Hello,
Can anyone help me with making some changes to a AVERAGE formula?

I need a average formula that includes the values of price every four hours over the last five instances,current price included.

Below is formula I've been working with. I'm thinking adding an Offset or IsNumber might be the best way to go because it'll allow me to skip between the prices and only factor in the prices I want.

That's the gist of what I'm trying to do, be able to include any combination of numbers in a average formula without the numbers having to be in continuous order.

Basic Average Formula:

=AVERAGE(B3,B7,B11,B15,B19)

Please see attached spreadsheet for a better understanding.
Thanking you for taking the time to read this post and for any and all help you can provide.