I sounds as though there might be too many dependencies. Excel keeps track
of equations to determine which cells have to be recalculated when a cell is
changed. after so many dependencies, Excel just recalculates all of them at
each change. needless to say the speed of operation slows down dramatically.
Look for large blocks of formulas which are not dynamically needed at all
times. and think about using a macro to populate those cells just when
needed.

Large lookups both add dependencies and time per calculation
Simplifying equations and sometimes seting up a hierarchical series of calcs
can sometimes speed up recalcs dramatically
"Andrew C" wrote:

I have constructed a spreadsheet with a number of formulae and lots of data,
and it seems to be taking ages to calculate. Has anyone any tips to speed up
the process.
Thanks