Depends on what version of the software you're using, Tom. The simplest would perhaps be that, if you've got CC2013, create a filtered view containing just the requirements added in that time frame, then generate a report (from the filter) on those.
There are a couple of alternatives, too. Check out the Excel "Dashboard" template - it does what you're looking to in the Additions/Modifications section (row 21 specifically) using Excel formulas.
If you'd instead like a dedicated Word template (or you're not using CC2013), you could set up a parameter for your date to check against. It's not as automatic as an Excel report, but you could use it like this:
Requirements created since $$CreatedDate
$repeatRequirements where DateAdded >= $$CreatedDate
$Name $ID
$endrepeatRequirements
$info
$param $$CreatedDate
$endinfo