XLR sample - sales report by item by sales rep

Hi all,

I am using the above report at client site and its working great.

The cust now has a requirement to modify this and include a column that looks at same period -12mths.

I can easily do that by -

- duplicating the existing columns

- applying period parameter to columns and not the report default

- and changing the parameter to be @per-12.

This doesnt seem to work however as the parameter is an expression which means I can select a range of periods. XLR gives error:

Definition parsing failed: syntax error near @per-12.

It only seems to work when I have the parameter as a dimension so that only 1 period can be selected.

Can XLR do the calculation for the range of periods -12 mths?

My client wants to create a quarterly report so selecting 1 period is not going to be sufficient.

I hope what I have explained is clear.

Thanks for any advice,

John