how to create a year-n variable in BEX

Hi experts,

I need to create 2 variables in bex that :

1- allows to filter the interval of year : [2000...input year]

Example, when lunch the bex query :

input year : 2008

the answer for the data is between 2000 and 2008

2- allows to filter input year-1

I dont want to do this using sap exit.

Thanks for your help

Raed