I have a very large table on a sheet named "Data". One column has date, one
has provider, one has type, one has county (in other words, multiple sort
criteria), along with about a hundred columns with provider data.

My staff wanted a customised report that would, by question, sumarize last
years data vs. this year's data, vs. this months data. They also wanted this
by county and by provider and by type. (In other words, a report that looked
at the Data sheet and made many, many, many caculations).

I created a canned report sheet, that ties to a worksheet sheet. This
worksheet has about 30 rows by 100 columns of array formulas which make all
the necessary calculations. While this ultimately does what I want, it is
very slow while calculating. Does anyone have a general suggestion to point
me in a different direction. I have tried using DataSum, but it hasn't
proved effective.