What filters to use in pivot table

Hi,

I have a very large amount of data that can only be downloaded one way and due to time constraints and the very large amount of data I prefer not to rearrange it. The first column includes a Student Number but this may appear many times due to changing data in other columns.

How do I count the students once only. What filters do I use? In my small sample the answer should be 2.

Student Number *** School District Status Year Enrolled From Enrolled To
123456 F Smithfield North Enrolled 2011 31/01/2011 8/04/2011
123456 F Smithfield North Enrolled 2011 27/04/2011 6/05/2011
123456 F Smithfield North Enrolled 2011 9/05/2011 18/11/2011
123456 F Smithfield North Enrolled 2011 21/11/2011 23/12/2011
787878 F Smithfield North Enrolled 2011 31/01/2011 8/04/2011
787878 F Smithfield North Enrolled 2011 27/04/2011 6/05/2011
787878 F Smithfield North Enrolled 2011 9/05/2011 18/11/2011
787878 F Smithfield North Enrolled 2011 21/11/2011 23/12/2011

I have struggled with this for years, any suggestions would be appreciated.

Regards,

I have not yet tried your suggestion - but thought I would have a go at attaching the file anyway. If you have time it would great if you could take a look.

Thanks for your quick response.

Sorry - I should have also said that I may want to count how many students were enrolled in Smithfield school for e.g. and this result would be 2.