Variance Calculation Question


Hey All, I'm trying to calculate variance on some usage data with multiple  calculations. 

I need to be able to calculate the average of the 5 prior same days of the week. 

For example for the date of 8/16 to find the variance I would need to compare the average of 8/9,8/2,/7/26,7/19,/7/12.

I also need to pull in average and total for the current day as well has  show variance over 5% and anything negative. 


I've tried a bunch of things but can't see to get anything to calculate properly. 

Any help would be appreciated. Thanks!