Dynamic ALV Field Catalog and Values

Hello Experts,

In my selection screen, there is a select options which is a reporting period.  The reporting periods can be from 1 to 7.

So I have to display an ALV based on the values inputed on the selection screen and the values I am taking from KNC1.

Here is the screen shot of table knc1. So i have to take values as mentioned in the screen shot.

So if user enters 1 = 1 (The first set of Debit credit and Balance in the KNc1 table 1,2 and 3 coloumns).

                          2 = 4 (Records from the f 4,5 and 6 coloumns)

                          3 = 7 (Records from 7,8, and 9 coloumns)

                           4=10 (Records from 10,11,12 ) and so on.

So how i have to build a field catalog and alv table values based on this.

Regards,

Marina.