How can I create spirals of numbers quickly?

Hello, I am very interested in maths and i wanted to use Excel to look into some number series. I have been putting numbers in spirals in excel, highlighting the prime numbers and looking for patterns. Instead of the spiral counting up though, the spiral starts with any number and counts down to one.

This is an example of one of the spirals i was working on where the spiral starts at 997(highlighted in red):
spiral.jpg

My problem is that it takes ages to manually type a spiral like that. My question is whats the quickest way to insert a spiral like this into excel where i can choose the center number. Eventually I am aiming to compare many different spirals with different center numbers. Also ( if its not too much to ask) is it possible to get Excel to automatically highlight the prime numbers?

As you can tell I am very new to Excel and any help would be greatly appreciated.

Really intriguing question this. Give this code a go. I can't take credit for it - came from Peter_SSs

http://www.mrexcel.com/forum/excel-q...er-system.html

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This is probably the coolest question I've seen here in years.

I got this far before my brain exploded and I checked for an update. So glad someone else solved this.

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