Re: "I have to say Excel is one thing Microsoft got right."
You know what, you make an extremely valid point. I have transferred a lot of what I have done over the years to SQL because it makes sense however there were other occasions where it didn't. Excel still has it's place though because of what it can do in it's own ecosystem. Where else could I take raw data out of a database, manipulate it, get crystal reports to create the report and then email it all automatically with the click of a button?
Turn off auto-calculation and use F9 to calculate. This goes back to my response above, there are things you can but should not do in excel and from the sound of what you are describing it should not be done in excel. Personally I join multiple systems into a database and then create report data which is then used to generate the reports via excel, the grunt work has already been done and takes about an hour. I could have done it all in excel but that would just add a ridiculous amount of time to the process. I don't think I've come across a calculation you can't replicate in SQL though I'm probably wrong.