Right-click on the report and choose Clone
Provide it with a new name
In the right pane, click Edit
Just above the ORDER BY, on a new line, add this text:
AND isw.InstallDate BETWEEN GETDATE() - 30 AND GETDATE()
Click Save Changes
Does this do it?
Oops, just noticed you said 'X' days, not 30 days.
After clicking Edit, instead of adding the WHERE clause I provided, click Report Parameters, and click Add and choose New Parameter
For the name, type Days
For the description, Number of days to include
For Type, choose Basic Int16 Integer
For default value, choose 30 (or whatever you like)
Choose Basic Parameter Value Edit Control from the drop-down
Click OK
Under the Data Source tab, under the Parameterised Query tab, within the WHERE clause, just above the ORDER BY clause, add this new line:
AND (isw.InstallDate BETWEEN GETDATE()-%Days% AND GETDATE())
(The name Days is case sensitive.)
I had a bug in my XML where the Days field wasn't showing for editing prior to running the report, so I was stuck with my default value until I found this:
http://www.symantec.com/business/support/index?page=content&id=TECH44346
I hope this helps.