Your relationship would look like this:
MainTable::IP > Countries::NumberFrom AND
MainTable::IP < Countries::NumberTo
You can use this relationship to specify a LookedUP value on a CountryName field in MainTable or you could simply place the Country field from Countries on your MainTable layout.
... and relookup:-)
Thanks, you're a genius and a gentleman for the quickest reply and almost making me fall in love with FM again:smileyvery-happy: