this is long, and I apologise if my meaning isn't immediately clear

I have a template used by our group to do bulk calculations - this is an
ongoing project/learning tool for me and so far it's been quite
successful (on both counts), but...

Previous incarnations used a series of (nested) IF functions (up to about
10 separate calculations per row), but over time these were becoming
increasingly complex and unwieldy. Another disadvantage was that the
resulting filesize was considerably larger (40-60M workbooks are common).

In an attempt to reduce a) bloat, b) complexity, c) duplication I have
converted most of the formula's to VBA functions - while this has effectively
reduced the number of formula's used (instead of using the same formula with
different variables each cell in each row, each cell now calls the vba
function and passes the relevant var) it has introduced a substantial deficit
in speed (sheets routinely have 50K+ records and recalculation now takes 5-10
minutes)

what I'm looking for now (finally, I hear you say) is some way to speed
things up - this is a tool that is used daily by about 20 users and that sort
of response time is way too long (if this is not possible I'll be forced to
go back to doing things to 'old' way...)

any/all ideas gratefully received

many thanks (in advance)

S
--
Instead of building bigger and better weapons of mass destruction, we should
be trying to get better use out of the ones we've already got....