Excel is my life right now......

Subtotal Function in Excel
http://www.exceltrick.com/formulas_macros/subtotal-function-in-excel/
http://spreadsheetpage.com/index.php/tip/count_autofiltered_rows/

And more vlookup stuff
http://spreadsheets.about.com/od/excelfunctions/ss/vlookup.htm
http://www.howtogeek.com/howto/13780/using-vlookup-in-excel/?PageSpeed=noscript

ISNA
http://www.techonthenet.com/excel/formulas/isna.php

MS Excel: ISNA Function 

Used to check for a #N/A (value not available) error.

Syntax

ISNA( value )

Parameters or Arguments

value

The value that you want to test. If value is a #N/A error value , this function will return TRUE. Otherwise, it will return FALSE.