diff --git a/addons/hr_timesheet_sheet/hr_timesheet_sheet.py b/addons/hr_timesheet_sheet/hr_timesheet_sheet.py
index 83ce4f5168f..4ca8400aaaf 100644
--- a/addons/hr_timesheet_sheet/hr_timesheet_sheet.py
+++ b/addons/hr_timesheet_sheet/hr_timesheet_sheet.py
@@ -205,8 +205,10 @@ class hr_timesheet_sheet(osv.osv):
         return True
 
     _columns = {
-        'name': fields.char('Description', size=64, select=1),
-        'user_id': fields.many2one('res.users', 'User', required=True, select=1),
+        'name': fields.char('Description', size=64, select=1, 
+                            states={'confirm':[('readonly', True)], 'done':[('readonly', True)]}),
+        'user_id': fields.many2one('res.users', 'User', required=True, select=1,
+                            states={'confirm':[('readonly', True)], 'done':[('readonly', True)]}),
         'date_from': fields.date('Date from', required=True, select=1, readonly=True, states={'new':[('readonly', False)]}),
         'date_to': fields.date('Date to', required=True, select=1, readonly=True, states={'new':[('readonly', False)]}),
         'date_current': fields.date('Current date', required=True),
@@ -297,6 +299,12 @@ class hr_timesheet_sheet(osv.osv):
                 for r in self.read(cr, uid, ids, ['date_from', 'date_to'],
                     context, load='_classic_write')]
 
+    def unlink(self, cr, uid, ids, context=None):
+        sheets = self.read(cr, uid, ids, ['state'])
+        if any(s['state'] in ('confirm', 'done') for s in sheets):
+            raise osv.except_osv(_('Invalid action !'), _('Cannot delete Sheet(s) which are already confirmed !'))
+        return super(hr_timesheet_sheet, self).unlink(cr, uid, ids, context=context)
+
 hr_timesheet_sheet()