You will need to make your own custom CAN message to get the setpoint from the screen to the MC24, and another custom CAN message to get the measured pressure value from the MC24 to the screen. The MC24 should handle all the pressure control calculations.
Under the GUIDE component tab, have a look at the Connection->CAN->Transmit CAN block and also the Receive CAN Basic block. Read the documentation for both of these.
I would have two button inputs on the screen feed an up/down counter block in the screen program. The output goes to a your CAN transmit block with a unique message ID. In the MC24 software, a CAN receive block has the same message ID and a permissive mask value, and the data from this block goes to the pressure control as your setpoint. The pressure control consists of a PID block where you can initially set the 'I' and 'D' gains to 0 just to get proportional control at first. The pressure is measured with a Danfoss pressure sensor that is connected to the MC24, and is the feedback to the PID block. The measured pressure also goes to a CAN transmit block with another unique message ID, and the screen has a matching CAN receive block for getting this value and sending it to a screen block for display.
