Hi Jan,

Try this example code 

class CRMleadInherit(models.Model):
    _inherit='crm.lead'

    amount = fields.Float(compute='_compute_expected_revenue', store=True)

    @api.depends('order_ids')
    def _compute_expected_revenue(self):
        for rec in self:
            if rec.order_ids:
                last_quotation = rec.order_ids[0]
                rec.amount = last_quotation.amount_untaxed
            else:
                rec.amount = 0.0

​Here in this field amount have the calculation that you needed

Regards

Hi Julien

No not yet... 

We asked our Odoo partner to have a look at this, because they did some programming on top of this field.