Best reading of 7 days in webi

Hello Guys,

I have a requirement where I need to calculate best reading of seven last days.

So for example today is  Oct 2  and data is something like following:-

Date        Reading

Oct 1        10.3

Sep 30      15.3

Sep 29      12.3

Sep 28      17.5

Sep 27      11.26

Sep 26      9.23

Sep 27      15.0

In above example I would just want to see Sep 28 values in the table.

How can I do that?

Report has 45 days worth data.

Please suggest.

Regards

Ajay