l10n_lu_ext/views/res_company.xml
<?xml version="1.0" encoding="UTF-8"?>
<openerp>
<data>
<record model="ir.ui.view" id="view_company_form">
<field name="name">res.company.form (l10n_lu_ext)</field>
<field name="model">res.company</field>
<field name="inherit_id" ref="base.view_company_form"/>
<field name="arch" type="xml">
<xpath expr="//field[@name='vat']" position="before">
<field name="l10n_lu_matricule" attrs="{'invisible': [('country_id', '!=', %(base.lu)d)]}"/>
</xpath>
</field>
</record>
</data>
</openerp>