Hi there,
 
I'm searching for a solution to add trendline in my charts.
For example: I have a chart which shows the Sales per week. Every week is shown in a bar.
Our Sales dept. is interested in have a trendline showing the average sales of the selected period (let’s say 4 month or 20 weeks) in the same chart.
 
Changing the the selected period has to lead to a new calculation of the average.
 
Any idea?
 
Regards,
Jörn