Work with specific fields, based on user input

Hi,

I am extracting all data from table FMGLFLEXT. First, I will go in and extract data for the year that the user has entered on the selection screen.

However, the user will also enter the prior period & current period. These periods have to do with the fields between TSL01 and TSL16. For example, if the user enters 2 and 7, I should only work with data between fields TSL02 and TSL07.

How is this possible?

Please help.