need help on this:

NAME DATE

dan 01/01/2005
ran 02/01/2005
dan 03/01/2005
shon 10/1/2005
dan 20/01/2005
dan 21/01/2005
dan 23/01/2005

i need to count how many unique names are between two dates
for example between 01/01/2005 and 10/1/2005 there is 3 (dan,ran,shon)

thans for your help

shinbar