Weather-dependent heating temperature control

Good afternoon.

I need your help . it is necessary to implement weather-dependent temperature control in the heating system on the Logo. There are two temperature sensors, one outside, the second in the heating pipe, there is also a boiler that heats the heating system. I need to make it so that there is a linear graph of temperature changes in the heating system, for example, if it is -20 outside, then the heating system is 95, and accordingly if it is +10 outside, then the heating system will be 40 degrees Celsius. Previously, I used separate control devices to implement this function, and now I decided to do it on the logo, but I can't organize the scaling correctly. Please, if someone has already done this or knows how, you can show an example.