Heating Control + input_slider + template

Hi all,

In my Automation, I control my HVAC with a relay (on/off) on when under a temperature, and off over a temperature.
I want to introduce the temperature value with an input_slider, but I don’t know a to use template to wrok with the trigger/below.
here is my code for understanding:
code automation.yaml :

  • alias: ‘trig temp basse presence’
    trigger:
    platform: numeric_state
    entity_id: sensor.sonde_14_1
    value_template: ‘{{ state.attributes.V_TEMP }}’
    below: 18.9
    action:
    • service: homeassistant.turn_on
      entity_id: switch.chaudiere_15_0

How can I replace 18.9 by (input_slider value -0.1)?

Some one have an idea?
Or this is not possible with HA?