Well, kinda.
The [Number Plays] field is just a simple counter. It doesn't track date/time on a per-play basis. It is the total count of plays since the file was imported. However, you do also have the [Last Played] field, which tracks the most recent time a particular item was played.
So, you can do something like:
[Media Type]=[Audio] [Last Played]=<14d ~sort=[Number Plays]-d
This will show any file that has been played in the last 14 days, sorted with the files that have the most total number of plays (since they were imported, not number of plays in the past 14 days) on top.
Another, perhaps more useful example would be something like:
[Media Type]=[Audio] [Last Played]=<36w ~sort=[Number Plays]-d,[Last Played]-d ~n=300
In this case, the file has to have been played in the last 36 weeks to make the cut at all. Then, that list is sorted with the files that have been most played on top, then limited to the top 300 results.
I use this latter one in a Smartlist called Most Played (Recent Only).
What you can't do, is count only the [Number Plays] that have occurred in the past <arbitrary time period>. MC doesn't track a Date/Timestamp when each play in [Number Plays] occurred, but only the most recent play's Date/Timestamp and the overall total number of plays.
Make sense?