Returning an error message when a data value entered is not within range

Hi all,

I'm attempting to create an invoice workbook for a school assignment that uses vlookup to find a customer and their details, and then in a table below, works out prices of orders. The system is working great, and I have no errors with it at the moment, but part of the requirements for the invoice is that it must be 'idiot proof'. What I want to do, is if a value greater than 10 is entered in any of the yellow cells in the 'Stock Code' column, return an error to the user stating that they must enter a value between 1-10. The 1-10 in this instance refers to a stocklist on the next sheet, which has a numbered list, 1 being Basketball, 2 being Netball and so on, up until 10. If a number greater than 10 is entered in the 'Stock Code', how do I politely tell the user?

Sorry for the vagueness as I am still getting my head around using excel. If you need further details, just let me know. Thanks for your help Capture.PNG

Thanks heaps AndyLitch, worked like a charm