Re: "I have to say Excel is one thing Microsoft got right."
"but what boils my piss is the fact that if you then try to interact at all with it... it starts the whole bloody calculation again (or so it appears)!"
a) Learn to use the software properly, and turn off automatic sheet recalculation. Just because the software makes it all look "dead simps" doesn't mean you can get clever without doing some reading of the manual. See: post #1 in this thread.
2) Are you sure you ae using the right tool for the right job? Hundreds of thousands of rows? This isn't what spreadsheets are for. You can make them work that way, but the user experience is a diminishing returns calculation inversely proportional to the data density.