Display images for fixed time

Hi everyone,
I want to display pictures for fixed time. so I defined the "Auto-advance after" to 8 seconds, and to prevent the subjects from advancing by clicking on next button, I defined the "Enable submit after" to 15 seconds.
But it is still possible to move forward by pressing "enter".
I tried to disable it by using the next script:
Qualtrics.SurveyEngine.addOnReady(function() {
this.hideNextButton();
});
and this too:
Qualtrics.SurveyEngine.addOnload(function() {
this.disableNextButton();
});
but I still can move forward by pressing enter.
note: I want to prevent the possibility of advancing only in some of the questions in block, so I can not use embedded data.
any suggestions?
thanks!