Calculating Threads

[ExcelAtEverything]

Hello,

I'm new to PQ, and noticing that when working in a very hefty, data-heavy sheet, Excel keeps freezing when something shows at bottom of screen "calculating theads". Then it starts at 0% and excruciatingly sowly starts moving up to 1%... then 2%, etc. What is happening, and is there anything I can do to mitigate this?
(If the answer is to 'lighten the load' by switching to Microsoft Access as a database, I don't have the means to do that at this point, so is there another way?)

Thanks!