account_move_voucher/views/account_move_view.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <record id="view_move_form" model="ir.ui.view">
            <field name="name">account.move.form</field>
            <field name="model">account.move</field>
            <field name="inherit_id" ref="account.view_move_form"/>
            <field name="arch" type="xml">
                <button name="button_validate" position="after">
                    <button name="action_create_receipt_voucher" attrs="{'invisible':['|', ('state', '!=', 'posted'), ('receivable_residual', '=', 0.0)]}" string="Create Receipt Voucher" type="object" class="oe_highlight" groups="account.group_account_invoice"/>
                    <button name="action_create_payment_voucher" attrs="{'invisible':['|', ('state', '!=', 'posted'), ('payable_residual', '=', 0.0)]}" string="Create Payment Voucher" type="object" class="oe_highlight" groups="account.group_account_invoice"/>
                </button>
                <field name="amount" position="after">
                    <field name="receivable_residual" attrs="{'invisible': [('receivable_residual', '=', 0.0)]}"/>
                    <field name="payable_residual" attrs="{'invisible': [('payable_residual', '=', 0.0)]}"/>
                </field>
            </field>
        </record>
    </data>
</openerp>