barcode_purchase_order/views/purchase_order_search_box.xml

<?xml version="1.0" encoding="UTF-8"?>
<openerp>
	<data>
        <record id="purchase_order_product_search_view" model="ir.ui.view">
            <field name="name">purchase.order.product.search.view</field>
            <field name="model">purchase.order</field>
            <field name="inherit_id" ref="purchase.purchase_order_form"/>
            <field name="arch" type="xml">
                <field name="order_line" position="before">
                    <div class="purchase_product_search_box" attrs="{'invisible': [('state','not in',['draft','sent'])]}"></div>
                </field>
            </field>
        </record>
	</data>
</openerp>