How Do I Supress Validation Message Box?

This is how my form is set up

1) I have a checkbox "A" in the main subform1

2) I have 15 checkboxes in another subform2 (hidden initially)

3) when checkbox "A" in subform1 is selected/checked, subform2 unhhides itself and allows users to select one or more checkboxes in subform2

4) in the validate event of subform2, I have a script that checks to see if there are at least one checked checkbox selected, if so it returns true (valid) or else it returns false (invalid)\

My question is, if I don't check any of the 15 checkboxes in subform2 (obviously fails the validation script), and I execute xfa.form.execValidate(), it would pop up a message box saying "The value you entered for  is invalid".

If I click OK, then it would then pop up rest of the error messages from other fields.   I do not wish to see 2 pop ups when doing validation.

How do I supress the validation error popup for the subform2?

Thanks in advance.