sumproduct for two ranges

Hi, I hope someone can help me here.

I'm using 2003 and I am trying to use sumproduct for the following but having no luck.

I have a list of dates (C2:C31) running from 01/02/2014 to 02/03/2014.

I have a list of varying ages (D2:D31)

K11:K15 has age ranges, e.g. 18-25.

I need to take a date range of 01/02/2014-28/02/2014 then count how many occurrences of 18-25 there are in that given date range (the formula being in L11)

I can sumproduct a date range but I cannot lend it to an age range if you will.

I've posted a dummy book if someone could have a look.

I hope someone can help, googling and cobbling together formulas has not helped my cause!

Thanks