Field comparison validator

Great module, very effective.

However, may I suggest two more validators ?

1) It's presently possible to match a field against another. It would be much more powerful to be able to make more generic comparisons between two fields. For example : compare two date fields to ensure one date is greater (or lower) than the other.

2) Probably more tricky to code : ability to compare a field value against its initial (form built) value in order to forbid illegal transitions. For example, forbid to decrease a date field value, forbid to increase an integer value by more than a certain increment, etc.

Maybe I'm wrong, but I think that, if not too hard to code, those features would be highly appreciated.