pos/pos_no_bank_statement/view/account.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
	
	<!-- account.journal -->
        <record model="ir.ui.view" id="view_account_journal_pos_user_form_inherit">
            <field name="name">POS Journal Inherit</field>
            <field name="model">account.journal</field>
            <field name="inherit_id" ref="point_of_sale.view_account_journal_pos_user_form"/>
            <field name="arch" type="xml">
                <field name="journal_user" position="after">
                    <field name="no_bank_statement" attrs="{'readonly': [('journal_user', '=', False)]}"/>
                </field>
            </field>
        </record>
    </data>
</openerp>