I don't really want to use a list for this data validation problem because I
have 240 items for the list. Six of those items I want to display a message
if they are entered. What kind of formula do I use for this or do I have to
use a list?

In addition (as long as I'm asking) if I wanted a warning message to come up
if the item number was invalid (I assume I need a list then) can you put two
data validation formulas for the same cell reference? I would want both of
the above conditions met with messages.