Hi,
It's always possible to create variables for 0FISCPER of type user exit (not "input ready" so processed at i_step = 2). It is quite easy to come to the appropriate time interval based on the other variable of type manual input
An alternative approach could be to add 0FISCYEAR and 0FISCPER3 to the data model of the InfoProvider. In the Transformation you can use the standard Time conversion rules to e.g. derive Fiscal Year from Fiscal Year/Period.
This will make it very easy in the BEx Query to use offsets. E.g. 0FISCYEAR minus 1 will result in last Fiscal Year.
Best regards,
Sander