Andrew

Assuming you have a column of invoice dates in column A and a column of
invoice amounts in column B. First invoice date is in D1 and last invoice
date is in E1. The following array formula will sum the invoice amounts
between date in D1 and date in E1.

=SUMPRODUCT(--(A1:A18=D1),--(A1:A18<=E1),B1:B18)

Note that since this is an array formula you need to use Ctrl+Shift+Enter to
enter formula. I assumed the array ends at the 18th row but you can change
it to whatever you need.

Dave

"Andrew" wrote in message
...
I have a summary sheet where I want to know show the sum of all invoices
paid
per month. In the "invoices" sheet I enter the invoices, the amount, data
paid etc.

I have tried to use sumif and, for the criteria, used dates as a serial
number to select any date range that is of interest.

Gives me an error and I'm out of ideas.

Andrew