Hi Drogo ( sorry u didn't make it to more sessions 
)
that Ledger above which Dinesh Kumar Rengarajan menitone is only relevant when New GL is activated. I think you didn't have New GL active or?
Please use simply in F.01 "Special evaluatioins" and field Alternative period selection ( for referenc use simply F1 ... it will show this example
Examples
Company code 0001 with fiscal year end 12
Company code 0002 with fiscal year end 09Calendar reporting period............. 01/01/1990 - 12/31/1990
The periods 1990/01 to 1990/16 are used as reporting periods for company code 0001 and the periods 1990/04 to 1990/16 and 1991/01 to 1991/03 are used as reporting periods for company code 0002. The same is valid for the comparison period.
I think this is what you want or?
Regards
Jan