Revert should be put the field back the way it was, but in my limited testing it blanks the field and then the cursor wont go back into it. The whole routine then crashes with an 'EOF' error message so it appears to me that the undo is operating on my 'append blank' command rather than just on the field. I am using optimistic buffering and the rule fires when I tab out of the field. I was under the impression that these rules did not fire until the record was committed and I was happy with that. On discovering that the rules would file as an equivalent to a field valid I saw the opportunity to remove a lot of validation routine code, but the presence of the Revert botton is completely unwelcome.