Make the submit button presence 'hidden', add a second button that performs the check box validation and if the validation succeeds, call 'click' on the submit button.
// form1.page1.subform1.callSubmitBtn::click - (JavaScript, client)
if (form1.page1.subform1.cb.rawValue == "0") {
xfa.host.messageBox("Please agree to terms and conditions.","Agree",0);
}
else {
form1.page1.subform1.submitBtn.execEvent("click");
}
Steve