Deadloss wrote...
Can anyone tell me what the role of the 'Validation' option in the dat
menu is?

is it

a) It checks the worksheet for errors in your formulae

or

B) It allows you to set the properties of certain cells so that
incorrect data cannot be entered and you are prompted with a message
about the 'allowed' contents of the cell/cells.

It's B, which online help states perhaps not clearly enough.