PageValidator and submit action

Hi,

I would like to check if some fields are filled, but "only" depending on submit button clicked by user.

My intention was to develop a PageValidator for each Form (or a single one Generic) and to get all form values and "which was the submit action choosen", but in my IFormPageValidator implemented class it seems that only arrives:

public boolean validate(Map<String, FormFieldValue> fieldValues, Locale locale) {

Please, anybody knows how can I do to apply validations depending on submit action executed? For example, in a form with two submit buttons ("Accept"/"Reject"), validate if all fields are filled only if user has clicked "Accepted".

Thanks in advance,