Count rows then insert formula based on row counts

Hello Forum,
I have a spreadsheet with data about what information in a database has been reviewed or not (data is reviewed on a “page” by “page” basis, per subject).

The data looks something like this:

SITE # SUBJECT #VISIT NAME VISIT DATE PAGE NAME PAGE STATUS REVIEWED?
1001 1001008 End of Study 06/15/2012 Hematology Monitored Yes
1001 1001008 End of Study 06/15/2012 Chemistry Monitored No
1001 1001008 End of Study 06/15/2012 Vital Signs Monitored Yes

1001 1001009 Screening 07/02/2013 Eligibility Complete No
1001 1001009 Screening 07/02/2013 Disease History Complete Yes
1001 1001009 Screening 07/02/2013 Liver Function Complete Yes


The number of rows per subject varies as a function of number of pages that have data in them and is therefore dynamic.
I need to provide some metrics about how many pages per subject have been reviewed and this information needs to be presented in percent (%) format.

So for a given subject, all the rows will equal total number of rows (totrows) and all the rows with YES in column 7 will equal number of reviewed rows (revrows). This will make my formula look like:

Percent of reviewed per subject = (revrows/totrows)*100

And I want this formula result to be displayed in the cell (blank row, column 7), so that my data now looks like:

SITE # SUBJECT #VISIT NAME VISIT DATE PAGE NAME PAGE STATUS REVIEWED?
1001 1001008 End of Study 06/15/2012 Hematology Monitored Yes
1001 1001008 End of Study 06/15/2012 Chemistry Monitored No
1001 1001008 End of Study 06/15/2012 Vital Signs Monitored Yes
% Reviewed 67%
1001 1001009 Screening 07/02/2013 Eligibility Complete No
1001 1001009 Screening 07/02/2013 Disease History Complete Yes
1001 1001009 Screening 07/02/2013 Liver Function Complete Yes
% Reviewed 67%

I am not sure where or how to start writing this sort of code, so I would appreciate help or if someone could point me in the right direction. The attached file displays the data more accurately. Thanks!