@numbers01,
I'm trying to figure out exactly what you're referring to.
Is the 300,000 a figure? Is it the number of rows in the spreadsheet?
Let's say it's the number of rows. If that is the case, make additional sheets (
right-click the tab at the bottom of any sheet, select
insert and select
worksheet) and copy/paste portions of your data into each of them. I suspect you'd want to separate them out by year, so sort by year first and then do your copying and pasting.
If it is a figure, then we'd need to understand the type of operation you're looking to do. Averaging? Find the highest number in a column? Standard deviation?