Hiding a field in quick create

Hello,

I'm having some problems hiding a field in a Quick Create form for my entity.

My code:

    Xrm.Page.getAttribute("oop_customername").setVisible(false);

My error:

    TypeError: Xrm.Page.getAttribute(...).setVisible is not a function

The problem might be that as the Quick Create is a drop down above the current page, its it not holding the attribute in the quick create form I need to hide? How can I get the hold of the Quick Create and then hide the field?