Mark,

Not a problem - few pointers:

-I think one of the reasons your original code was running very slowly was that everytime you deleted a line of code the entire sheet recalculated itself. This takes a bit of time when you have so many formulas in the sheet.

-Your original code assigned the same r1c1 formula to several columns individually, this was unneccessary, you could do it all in one go.

-When deleting rows, you need to loop backwards otherwise you will skip some.