How the enhance screen of extension BO display the same element?

Hi experts,

I extension two BO, add the same element: XMID.

The frist extension BO, element XMID:ProjectID; then enhance the screen. It is OK.

The second extension BO, because the same name, so the element can't name XMID, I use: [Reference] element XMID;

But the second extension BO, when I enhance the screen, , the XMID can not display, what is the problem?

How can I do ? It is Urgent.

Thanks.