How to hide the button of a text entry question in MC Questions?

Hi everyone, 
i already found this code: 
Qualtrics.SurveyEngine.addOnload(function() {
jQuery("#"+this.questionId+" .InputText").prevAll("label").hide();
});
which works perfectly für small sized textfields. I want to change the size of de textfield to middle or big, but then the code doesn't work.
Maybe you could tell me how to change the code, so he works for a "middle-sized" text field.
Thank you for your help!