Number Of Days Worked Over A Time Frame

I need to be able to calculate the actual number of days worked for an employee over a specific date range. I have a data sheet containing employee, transactions, and date of transaction (date only, does not include time). The actual number of days worked may fluctuate due to time off or holidays, so I need to be able to calculate this individually by employee. For example, with columns Employee, Transaction, & Transaction Date:

123 ABC 07/01/2009
123 ABC 07/02/2009
123 DEF 07/02/2009
123 GHI 07/02/2009
123 ABC 07/03/2009
123 ABC 07/07/2009
123 DEF 07/07/2009
123 ABC 07/08/2009
123 ABC 07/09/2009
etc....

Should return 4 work days for employee 123 over the date range 07/01/2009-07/07/2009