Thanks,
After try some codes, I finally solved it using a select field:
   .xml
    'sequence_lot': fields.selection([("seq1",'Product 1'),("seq2",'Product 2'),("seq3",'Product 4'),("seq4",'Product '),("seq5",'Bases')],'Secuencia a usar '),
<field name="sequence_lot" on_change="onchange_sequence_lot(sequence_lot)"/>
.py Function onChange, using the id of sequence choosen, is posible use the name too.
def onchange_sequence_lot(self, cr, uid, ids, sequence_lot, context=None):
    result = {}
    if sequence_lot == "seq1":
        seq_choosen = self.pool.get('ir.sequence').get_id(cr, uid, 103, context={} ) #Using id of seq.
        result['value'] = {'name': seq_choosen,}    
        #raise osv.except_osv(_('Warning!'), _('Seq Conteo %s.'%str(seq_choosen)))
    elif sequence_lot == "seq2":
        seq_choosen = self.pool.get('ir.sequence').get_id(cr, uid, 30, context={} )
        result['value'] = {'name': seq_choosen,}
    elif sequence_lot == "seq3":
        seq_choosen = self.pool.get('ir.sequence').get_id(cr, uid, 27, context={} )
        result['value'] = {'name': seq_choosen,}
    elif sequence_lot == "seq4":
        seq_choosen = self.pool.get('ir.sequence').get_id(cr, uid, 39, context={} )
        result['value'] = {'name': seq_choosen,}
    elif sequence_lot == "seq5":
        seq_choosen = self.pool.get('ir.sequence').get_id(cr, uid, 39, context={} )
        result['value'] = {'name': seq_choosen,}
    else:
        seq_choosen = {}
        result['value'] = {'name': seq_choosen,}
    return result
When you say you tried some options, did you try (not sure if syntax is correct here): "'name': lambda x, y, z, c: x.pool.get('ir.sequence').get(y, z, x.browse(y, z, [x.id]).sequence_to_use_field)" where 'sequence_to_use_field' is the fields.selection?