How to retest related fields when one changes?

[tslatt]

I have two related fields: expiration month (mm) and expiration year (yy). I have custom validators on both of them to make sure the value is in the correct format, within range, and that the combo mm/yy is not <= the current mm/yy.

The problem is this: If today is 02/16 and I enter 02/16, it will correctly give me an error for month and year, saying it's expired. If I then change the year to 17, so now it is 02/17, changing the year triggers the year validation which succeeds, but I still have the error message under month saying it's expired.

How do I trigger re-validation of the month field after the user has changed the year field?

[tslatt]

I still need an answer on this. Anyone?

[tslatt]

Over a year later and I still need this. Does anyone know how to re-validate a single field without submitting or re-validating the entire form?