Hi
I'd manage a new field from "account.analytic.line"

class AnalyticLine(models.Model):
    _inherit = 'account.analytic.line'
   effective_unit_amount = fields.Float('Effective Quantity', default=0.0,)

I overrided the form view
<?xml version="1.0" encoding="UTF-8"?>
<openerp>
      <data>
             <record id="extended_view_timesheet_form" model="ir.ui.view">
                    <field name="name">Line creation and edition from grid</field>
                    <field name="model">account.analytic.line</field>
                    <field name="inherit_id" ref="timesheet_grid.view_timesheet_form"/>
                    <field name="arch" type="xml">
                            <xpath expr="//field[@name='unit_amount']" position="after">
                                     <field name="effective_unit_amount" string="Time Spent" widget="float_time"/>
                            </xpath>
                    </field>
             </record>
       </data>
</openerp>

but I receive
     raise ValueError(message)ValueError: Can't validate view:
     Field `task_id` does not exist

I can not understand the reason, because the "task_id" is a field of "account.analytic.line" model.
Anyone can help me?

Thank's
P.