I'm currently using the following formula to calculate certain cells in the
range only if they match in two columns. It works fine for getting a grand
total.

=SUMPRODUCT(--Logbook!T3:T65536<""),--(Logbook!U3:U65536<""),Logbook!T3:T65536))

But I'd like to be able to break this down by month in the date column.

Ex:

A B C
3-Jan 15 30
5-Jan 8 8
3-Mar 13 19
9-Mar 5 5
7-Jul 10 10
2-Jul 6 4

The values in columns B & C must match in order to be accepted. I'm stuck on
how to break it down by month only.

Not sure if this is important or not but not every row has a date or figure.

As always, help is greatly apprreciated!