purchase_order_agroyguazu/views/purchase_order_view.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <!--
            PURCHASE ORDER
        -->
        <record id="purchase_order_line_total" model="ir.ui.view">
            <field name="name">purchase.order.line.total</field>
            <field name="model">purchase.order</field>
            <field name="inherit_id" ref="purchase.purchase_order_form"/>
            <field name="arch" type="xml">
                <!--
                    PURCHASE ORDER
                -->
                <field name="picking_type_id" position="after">
                    <field name="contado" attrs="{'readonly':[('state','in',('approved','done'))]}"/>
                    <field name="credito" attrs="{'readonly':[('state','in',('approved','done'))]}"/>
                    <field name="invoice_number" attrs="{'readonly':[('state','in',('approved','done'))]}"/>
                </field>
                <!--
                    PURCHASE ORDER LINE
                -->
                <xpath expr="//tree[@string='Purchase Order Lines']//field[@name='price_subtotal']" position="after">
                    <field name="amount_total" readonly="1"/>
                </xpath>
                <xpath expr="//tree[@string='Purchase Order Lines']//field[@name='date_planned']" position="attributes">
                    <attribute name="invisible">1</attribute>
                </xpath>
                <xpath expr="//tree[@string='Purchase Order Lines']//field[@name='name']" position="attributes">
                    <attribute name="invisible">1</attribute>
                </xpath>
                <xpath expr="//tree[@string='Purchase Order Lines']//field[@name='product_uom']" position="attributes">
                    <attribute name="string">Unidad de Medida</attribute>
                </xpath>
                <!--
                    BUTTONS
                -->
                <button name="bid_received" states="sent" position="after">
                    <button name="purchase_process_now" string="Procesar Compra" type="object" states="draft,sent" groups="base.group_user" class="oe_highlight"/>
                </button>
                <button name="print_quotation" position="attributes">
                    <attribute name="invisible">1</attribute>
                </button>
                <button name="wkf_send_rfq" position="attributes">
                    <attribute name="invisible">1</attribute>
                </button>
                <button name="purchase_confirm" position="attributes">
                    <attribute name="invisible">1</attribute>
                </button>
                <button name="wkf_send_rfq" states="approved" position="attributes">
                    <attribute name="invisible">1</attribute>
                </button>
            </field>
        </record>

        <!--
            ACCOUNT INVOICE
        -->
        <record id="account_invoice_supplier_cred_cont" model="ir.ui.view">
            <field name="name">account.invoice.supplier.cred.cont</field>
            <field name="model">account.invoice</field>
            <field name="inherit_id" ref="account.invoice_supplier_form" />
            <field name="arch" type="xml">
                <xpath expr="//field[@name='journal_id']" position="after">
                    <field name="contado"/>
                    <field name="credito"/>
                </xpath>
            </field>
        </record>
    </data>
</openerp>