Here's a thread using a similar formula and I try to explain how it works...

http://www.excelforum.com/excel-work...ml#post1833718

The Countif() part is replaced by the Sumproduct() function reference to F1 in your sheet... it makes for a little better efficiency to have the Counting formula in a separate cell so that it is calculated once and not every time the array formula is copied to another cell.

The + sign between arguments is an array formula's way of saying "OR"... so if one argument or the other is true, then count.

see if it helps..

If you need further clarification please ask.