where can I find information on ........

where can I find information on doing calculations etc in access, and what all the complex functions do? it's not covered well in most books, they look at simple queries. is there a good web resource? basically I need to set up some kind of online financial tracking system and do calculations - invoices in and out month by month etc. to pinpoint when we'll have cashflow problems.

Any ideas/suggestions greatly welcome!

thanks, neil