I currently use the following formula to add values together from one tab to
a totals page.

=SUMPRODUCT(--('1-500'!C4:'1-500'!C518="CY"),--('1-500'!H4:'1-500'!H518="Bus"),'1-500'!G4:'1-500'!G518)

But I have added another page (tab) which i need adding into the totals
pages as well. The same information is held on this new page and it is held
in the same column and rows. How do i adjust the above formula to include the
new page? The name page is called 501-1000.

Thanks