Continuous 7 Day Average

I have recently been diagnosed with diabetes. I have a simple spreadsheet that I am keeping track of my blood sugar levels when I take it. I take it 2 - 3 times a day. I have 3 columns, A = Date B = Time C = blood sugar level. I have a simple average formula of the all the entries in Column C, but I would also like a rolling 7 day average. I can do this manually, but I dont want to have to keep modifying the simple average formula to do so. I am sure there is a way to do it with a formula that looks at the dates in Column A and then averages the numbers in Column C for those 7 days. I figure the tricky par is that Column A will have the same date for multiple rows. I can change the spreadsheet around if i need to, if it will make it easier. Something like having Column A only have a date entry for a single do, but I could have more columns for the blood sugar readings (morning, noon, evening, ect...). I would also like a 30 day average, but I assume I can just modify the 7 day formula to get that one going.

If anyone could help me out here, I would appreciate it. If you need more info, or if I did not explain it well enough, please let me know. Thanks...

Thanks for the reply.

Yes, I could do that for every 7 days, but I would like something that would update automatically so I dont have to keep modifying the formula, or creating a new one for every 7 days. Any ideas?

Correct, I want to see it as it changes over time. So I can just look at it and see that in the last 7 days, my blood sugar has be X number. So the 7 day average should change every day pretty much.