How to suppress client-side validation when field in bind to dojo's ajax call

Question

Using Struts 2 and Dojo

Given a Form with validate="true" for client-side validation, I have a form textfield that is bind to an Ajax action. When the field is changed the Ajax call should be executed (achieved by events="onkeyup"). Only the bound field is added to the Ajax call (using formFilter attribute).

But, the validation is executed before the Ajax call.

How can I achieve the Ajax action on the field without form client-side validation, and also client-side validation when the form is submitted?

10x to any effort.
I.