data across two different spreadsheets

Hi,
I have an interesting problem here.
There are 2 spreadhseets (.xls files). The first spreadsheet has a
columns which has either a Yes, No or NA in it.
What the second spreadsheet does is it counts the number of Yes and No
in that column of first sprsheet and calculates the % of Yes in it,
and displays it in a cell.
For example: B1 to B15, B18-B20.
Out of these 18 concerned cells in first spreadsheet, 9 are y rest are
no and there are no NAs say.
Then say cell B1 in second spreadshhet displays 50%.

So, the real deal is to collect data from another spreadsheet.

Thanks for any help.

-Sash.