Gebobs,
Thank you, that worked on that particular graph, but not on one I put together today, in fact there was no change.
It would appear that MS is removing functionality from the Office in little ways like this.

At one time whatever values you had in the XY columns appeared on your graph axis, but not now. Previously I used to put the date but over time MS corrupted that now I just use the nmber to represent the date and now that doesn't work.

It would appear that the functions on Excel now are there to allow you to make a pretty picture rather than construct a mathematical device as it was intended.
I have noticed that sometimes the Trend function is greyed out and cannot be used.

So what do I do next?