Jon Peltier wrote:
So the new data overwrites the old?

Yes, it is always being refreshed at a rate set by the user.

You could have a routine which copies
data after a recalculation event (which occurs when the data is updated) and
stores it onto another sheet.

This could be copy/paste with a timer?

Then you can chart these blocks of data as
separate series on a common chart.

Not sure what you mean as a novice?

Thanks for the feedback. This has been an age old problem of mine. At
least you have given me a guideline. For a novice, these problems are
horrendous, as there is virtually no material available, even in decent
Excel VBA books.

I have tried using macros before doing a copy/paste into another
worksheet, but they just seem to crash.

Could you give me an example of a routine, so then maybe I could modify it?