Creating a trendline based on previous 4 week average

[p4dd3]

Hello everybody,

I have data on a weekly level which goes from beginning of year until last week. I would like to also project how the next four weeks would perform based on the average last 4 weeks. I have tried several solutions here but I cannot get my numbers to add up, and in addition the formulas I have tried only work on day/month. Preferebly it could be a calculated column but also a measurement would be fine. My goal is to, in the same graph (line) display both the historical and the projected values - so for example last 3 weeks and upcoming 4 weeks. 

Thanks in advance for all help! 

My data looks something like this. Note that it is from appended Excels which creates some empty future date entries as below. The cells called "Order" are the ones I would like to fill for the last two weeks (in reality for upcoming 4 weeks).

Date	Week	Orders	Location
11/7-22	W28	50	A
11/7-22	W28	50	B
11/7-22	W28	100	C
18/7-22	W29	20	A
18/7-22	W29	30	B
18/7-22	W29	20	C
25/7-22	W30	30	A
25/7-22	W30	50	B
25/7-22	W30	100	C
1/8-22	W31	30	A
1/8-22	W31	50	B
1/8-22	W31	50	C
8/8-22	W32	30	A
8/8-22	W32	60	B
8/8-22	W32	70	C
15/8-22	W33		A
15/8-22	W33		B
15/8-22	W33		C
29/8-22	W34		A
29/8-22	W34		B
29/8-22	W34		C

[lbendlin]

see attached for one possible implementation. It sums the averages per location.