Magento Admin Layout – Adding a Block to New Order Page via Layout Update

On the frontend, I can successfully add a block using this layout update for my module:

<?xml version="1.0"?>
<layout version="0.1.0">
    <customer_address_form translate="label">
        <reference name="my.account.wrapper">
            <block type="core/template" name="customer_address_edit" template="customer_address_edit.phtml" after="customer_address_edit"></block>
        </reference>
    </customer_address_form>
</layout>

And then my customer_address_edit.phtml is rendered just fine…

However, on the admin side I'm having trouble. I'm trying to add a block in a similar way, to the New Order page. My layout file looks like this:

<?xml version="1.0"?>
<layout version="0.1.0">
    <adminhtml_sales_order_create_index>
        <reference name="order_item_extra_info">
            <block type="adminhtml/template" name="admin_order_create" template="admin_order_create.phtml"></block>
        </reference>
    </adminhtml_sales_order_create_index>
</layout>

I've tried a couple variations of that, like using core/template and setTemplate. I just want a block to be added where I can add some custom HTML or JavaScript in a phtml file. Does anyone know what's different about adding a new phtml block to admin vs frontend?

UPDATE: This layout worked (before_body_end):

<?xml version="1.0"?>
<layout version="0.1.0">
    <adminhtml_sales_order_create_index>
        <reference name="before_body_end">
            <block type="adminhtml/template" name="admin_order_create" template="admin_order_create.phtml"></block>
        </reference>
    </adminhtml_sales_order_create_index>
</layout>