Luc,
there are two possible solutions: Hack the metadata plugin by setting metaDone on the "toggled" element to false. That causes the metadata to be read again. I recommend a different approach: Use the required-with-dependency feature to make the validation more dynamic. You can use both jQuery expressions and functions as the argument to required, for example:
// required only when field #someValue is not blank required: "input#someValue:filled" required: function() { // only required when not the first option is selected return jQuery("select#month")[0].selectedIndex != 0; } I hope you get the idea, let me know if it works for you. Regards Jörn