Identifying 3 cells higher & lower vales & substract higher to lower values

Hi to All,

In a column three cell having some values, (e.x) 333, 444,555. First identifying

higher & values than higher to lower substract value, that is 555-333=222, this is the

answer, but i don't need the answer, only should alert POP a message if value is less than

250.

Thanks,

Regards,