Moving average 8 weeks

[#1]

Hello,

I must calculate 8 weeks moving average and not rolling average.

The calcul must start at the 8 weeks and move to the last week on the data.

It must calculate as "Excel moving average".

Why isn't works ? because it mustn't actualize on the date selection but actualize on the others selection.

I should display it on a chart with 2 others expressions with bars and the moving average on a line expression.

Thank you for your interest and help !