Message box with required fields

I have a check box, and when I check it I would like for another fields to be required. I seem to have that part working fine, so that when the user tries to submit the form without entering data into that field, it throws an error message.

I would like to take it one step further, that when the user TABS out of the field, it also pops up a message. And when the check box is NOT checked, then there would be no error message if the field is blank.

I put the following code on the field under the exit event:

if (this.rawValue == '' || this.rawValue == null || trainingCB =="1") {    xfa.host.messageBox("Training agenda required");}

However, the message box is popping up even when the check box is NOT checked. How do I get this to pop up only if the field is blank AND the check box IS checked?