Calculation Issue

Good afternoon everyone,

I am in the process of building a massive reporting 'portal' that pulls information on various measures from multiple sources across multiple brands and displays them all in one file. To provide my users with a friendly environment to work there are lots of dynamic charts controlled by an array of drop downs etc. To feed these charts i have an awful lot of longwinded formula's to allow such selections. At this time my file stands at about 18mb (the final published version will not be quite as big as i can paste values over the external data links once it is updated each day).

It should be noted at this point that i am aware that this may not be the most efficient way of doing things but its a tried and tested method in my company with the IT restrictions we have in place.

Of course with such a massive file i am having major issues with the time it is taking to calculate each time a change is made.

I have considered turning calculation off on open and then on/off when a change is made but this would be a bit longwinded (however if thats the only way then so be it) and would mean that all other files open for the users would be turned off (subsequently they would then start working on other things and saving reports all over the place with calculation off which would cause massive issues as they are marketing chaps and not very technical).

Is there another way to do this, ideally i would like to be able to turn the calculation off for my file only and then i can recalculate individual sheets/ranges as i need to. This surely would speed up my file ?

Any help/thoughts/input would be greatly appreciated.

Thanks

Chris