Hello  Yannick ,

You need to create wizard for the solution this problem and create method in it. like

Python Code -

from openerp.osv import fields, osv

from openerp.tools.translate import _

class refuse_leave(osv.osv_memory):

_name = "refuse.leave"

_description = "Leave Refused"

_columns = {

'refusal_explanation': fields.text('Refusal explanation', required=True)

}

def refuse_leave(self, cr, uid, ids, context=None):

abc_obj = self.pool.get('hr.holiday')

record_id = context.get('active_id')

data = self.read(cr,uid,ids)[0]

print data

xyz = data['refusal_explanation']

print abc_obj.write(cr,uid,[record_id], {'refusal_explanation':xyz,'state':'refuse'})

abc_obj.write(cr,uid,[record_id], {'refusal_explanation':xyz,'state':'refuse'})

return True

refuse_leave()

Xml code -

<?xml version="1.0" encoding="utf-8"?>

<openerp>

<data>

<record id="view_refuse_leave" model="ir.ui.view">

<field name="name">Leave Refuse</field>

<field name="model">refuse.leave</field>

<field name="arch" type="xml">

<form string="Refuse_Leave" version="7.0">

<group col="4">

<field name="refusal_explanation"/>

</group>

<footer>

<button string="Refused" type="object" name="refuse_leave" />

<button string="Cancel" class="oe_link" special="cancel"/>

</footer>

</form>

</field>

</record>

<record id="action_view_refuse_leave" model="ir.actions.act_window">

<field name="name">Leave Refuse</field>

<field name="type">ir.actions.act_window</field>

<field name="res_model">refuse.leave</field>

<field name="view_type">form</field>

<field name="view_mode">form</field>

<field name="target">new</field>

</record>

</data>

</openerp>

Hope it helps