Many thanks for that Ray.
I was expecting to do some weird complicated math with a unix timestamp.
I copied and pasted both your suggestions into DataAssist and up popped exactly what I was looking for.
All I had to do was display the results. I had no idea it was going to be that easy.
Oh... I had to change "SELECT * to "SELECT SUM(OrderAmount)"
...Nap time I think!
:)