How to use confirmation dialog in Odoo?

Question

I would like to get the value in the confirmation dialog box in the ode. I have a form with a choice. When I select a value in the list and click the "Save" button, I have a dialog box with a message. In this post, I would like to get the selected value. Any idea?

<button string="save"
        icon="gtk-ok"
        type="object"
        name="update_year"
        confirm="The selected year is XXXX. Confirm ?"/>