Great news.

There are a few examples of these types of gains on this board and in general all follow the same pattern that is to say:

-- sorting data (allowing for binary search methods)
-- use of basic & efficient helpers
-- avoiding multi conditional summary calculations en masse or in conjunction with large data sets (avoiding Volatility)

Charles Williams' site is excellent resource for all things calculation if you're interested in optimisation etc:

http://www.decisionmodels.com/optspeed.htm
http://www.decisionmodels.com/calcsecrets.htm