Spell check

Another gadget I should purchase is some kind of spell check that keeps me from:

1. making all the spelling errors on a post (where the word is actually spelled correctly but isn't the right word such as illusive/elusive and isle/aisle, but
2. not finding the errors until much later and
3. then just happening to catch them one by one over a period of hours, and
4. having to correct each one after the post has already been seen by anyone who sees these posts!