I am working on a reporting spread and need some help making a total.

Example of sheet:
Station ID Keyboard Mouse
----------- ----------- -------
S1 Missing
S2 Damaged
S3 Missing
S4

I currently have a SUMPRODUCT funtion where it will check the cells that if
it has no typing in Keyboard and Mouse fields then it will add a 1 to a
different area of the sheet where I will have a running total. (that is where
I have the SUMPRODUCT function).

How can I make it so I can use one cell and have the formula check the
spaces in S1, S2, S3, S4

Code I have right now:
=SUMPRODUCT(--(b3=""),--(c3=""))

Something like it will have an array where it will run the same function but
make it check b4 and c4 then b5 and c5