Code to calculate the last 720 valid hours THEN give a rollin average of the data

Ok so basically what I have is a list of hourly data for several months. What I need to do is calculate a rolling average of 720 hours of VALID data. All data in the spreadsheet is not valid so I would need the code to omit invalid data & hours (invalid hours are highlighted red and data is blank) and then calculate a rolling average of 720 hours of valid data. By rolling average I mean for example, if I start at 4/15/2012 @ 1300 I need an average of that next 720 hours of valid data and would need a new average of 720 hours of data starting at 4/15/2012 1400 and so on until the last hour of data I have is included.

Its been about a year since I've written any code this in depth so I really need some help from some of you pros on here.

Thanks and I have attached an example spreadsheet of the data I'm working with