heating circuit

hi, for my heating circuit i've got an program running to mix the return water with 80 degrees water from my accumulators (4000L) to a set value. this value is set with an analog threshold trigger. i'd like to change this on and off set value with the logo cursor key's and/or with an input. 

how can i set this value? i cannot connect an input to the parameter input of the thresholdtrigger.

example: now the temperature is set between 52 and 50 degrees. thats to hot and needs to be set lower to 42-40. this i want to do with an input or the cursor key's

@Moderator:

Move to LOGO! projects?

that was not really what i meant. 

i know thats possible, but i would like to have a designated button for raising and lowering the temperature. 

i still have 5 inputs free. so i can hardwire two switches if necessary, is it possible that way?

Okay, you want it with digital inputs.

Two setpoints = 4 DI.

Or you use two message texts, for every setpoint a message texts. Then need you only two DI. Or two cursor keys. But if you want make it with cursor keys, then note: For changing the setpoints with cursor keys, then have you to press ESC key + cursor key.

Tell what you want.

Two digital inputs connected to up/down counter.

The count value from the counters is connected to the on and off parameters of the analog threshold trigger.

Is this something close to what you were describing?