Call a helper to conditionally load a template

load_template_layout

 <adminhtml_sales_order_create_index>
        <reference name="shipping_method">
            <action method="setTemplate">
                <template helper="wsacommon/template/adminTemplate">
                    <arg>adminhtml_sales_order_create_index</arg>
                </template>
            </action>
        </reference>
</adminhtml_sales_order_create_index>