Speeding up a macro

I recorded and then modified a macro. It seems fairly easy but it takes like 20 or 30 minutes to run. It puts a formula in columns, autofills the columns and then copies, paste special values them all. I am wondering if there is a way to make it run faster. There are many columns with formulas that go through the process so i have to wonder if it's just too big and unavoidable.

I also don't really understand the process. In File - Options, Enable Multi Threaded Calculations and Use All Processors (4) is checked. Enable Iterative Calculation is unchecked and I have no idea what that means.

As the macro runs it shows that all processors are being used and works its way from 0% to 100%. It repeats the 0-100% part multiple times. I don't understand that. Why not just once? Why does it restart the calculations multiple times?

I am attaching the code in a workbook. It has no data or anything - just the code. Is it possible for anyone to look at the code and maybe suggest a way to make it run faster? If necessary I can attach a complete sample so the code can be run but I don't know if it's necessary.

Anything anyone can suggest to make it faster would be so, so appreciated by me.

Hi, Jeff

Thank you. I will make your Select change and check out the links you provided. I also just noticed that the range for the formula doesn't match the corresponding range for the autofill. I added a column a day or two ago. Fixed formulas, not autofill ranges. Although even before I messed that part up and it was running properly, it took forever. I will however fix the ranges, make your change and see what happens. And I'll check out your links. This Excel beast is such a struggle... But thoroughly enjoyable and addictive. The challenge... The conquer... But, oh so many pieces in the puzzle... Sigh. Let's see if I'm back here tomorrow night with a sample workbook. lol. Thanks again.