Custom Rules execution timing

Hello,

I have a dialog box that collects user information followed by a message box that has a custom rule associated with it so that the message box only displays if the rule is validated to true.

What I'm finding is that the custom rule on the message box is executed when the dialog box is first displayed not after they click next. the rule is then executed again when the next button is pressed. Is there a way to stop the early execution of the rule? the rule requires information in the dialog box which is why it is on a message box after the dialog box.

Thanks.