Analytics Software

Hi,
I am trying to create a report that selects data based on a filter on a DATE column, wherein the report displays records created in the last +'n'+ days (a variable limit). Is there a way where I can prompt the user to enter the "Number of days" and then use that value to subtract from SYSDATE and then select data where the date column is greater than this value, in the limit section?
The only way at the moment I can get it working is by using custom SQL in the Limit like: Issued_Date > trunc(SYSDATE) - 7 . However it is not a very elegant solution as the user will need to change the '7' to another random value every time and it does not give out a clear purpose. I would like that "day" value to be prompted and then used in the same manner as the spelled out condition above.
Any help is much appreciated.
Thanks!