Is there a way to find out how many times a certain term has been searched for in a certain timeframe?
You could try Google Trends or the new Google Insights for Search. They won't give you absolute numbers though, just comparisons.
There are scads of dodgy-looking SEO tools out there that do purport to give you more exact numbers. If you decide to buy any of them, you should consider trying the V1@gra I'm selling first.
I've found this page on Google Adwords.
You can filter on time and location.
You can see more information if you have an AdWords account.