Max/Min employees based on start/term date

I'm looking to calculate the maximum and minimum employees that we have had over the course of the year for varying hiring locations. Previously, I have just been calculating by hand (hire +1, term -1, hire +1, hire+1, etc) but this is time consuming as we have several hundred. I have the start and termination dates (if applicable).

Does anyone know of a way this can be done? My spreadsheet reflects data like:

Name, Date of Hire, Termination Date
EE A, 1/1/2007,
EE B, 7/8/2012,
EE C, 3/10/2000, 3/7/2012
EE D, 2/4/2010, 7/7/2012

If they have not been termed, there is no data in that field. Additionally, I will be starting at a base number as most people are already hired before this past year. So for the above data, the min would be 1 and the max would be 3 for 1/1/2012-12/31/2012. (start with A,C,D- lose C,D- gain B)

Bumping this to see if anyone can help