Vlookup and rolling 4 week average

Hi Guys,

Hoping someone can help.
I am trying to automate a spreadsheet....

I want a column to spit out data after matching a specific date and also automatically calculate the average for last 4 weeks on the same day!
for eg: If today is 23rd Jun - I want the column to pick this value and also the value a week before which would be 16th Jun. And then do the average of the last 4 weeks!

I tried vlookup and match but cant seem to figure it out.

Attached example...can someone help please.