Thanks for your answer. I could not understand the coordinates but that's my fault because I cropped them from the picture I have sent.

EXX.PNG

So if I take this table into account, what formula would I need to use in order to determine Mark's sales on 16/12/2018?

Also is it OK to use a Cell value to be looked up - i.e. B2 - (if value is exactly the same in the reference table) instead of the exact content in quotation marks - i.e. "John" or "16/12/2018"?

Cheers!