Variable on Bex Reporting

Hi Bex Experts,

I have Date (0PSTNG_DATE)  fields in my bex reporting, if  user enter the value  like 10 then  we need to display the < (current date - 10) records,

i.e

if user enter the value = 10, then desire output

like       Date              doc_number         Sales quantity

          14/06/2016           11111               76

          14/06/2016            11112              20

          13/06/2016           11234               90

          12/06/2016             76123              34

          11/06/2016 ................................

Currently I apply the Off set variable for date field but business  wants enter  the value  in dynamically .

Please suggest to me for resolving the issue

Best Regards

Srinu