Reference value in analog threshold switch

Hi all!

This is my situation:

I've 3 analog threshold switches that check the same AI (temperature). Each switch controls a heating but they should follow an order based on the first heating settings:

the first one should power on under a temperature (x) and power off over a temperature (y).

the second one should power on under a temperature (z = x+5) and power off over a temperature (k = y-5)

the third one should power on under a temperature (z+2) and power off over a temperature (k-2)

I've seen i can't use a formula directly in the threshold switch, so i found the function "mathematical operation" but i cannot use the ON value as reference becouse it only takes the Ax value.

Any ideas to connect the ON/OFF values?

Look at this Siemens Webside:

https://support.industry.siemens.com/cs/#document/109471094?pnid=13617&lc=en-DE

Or this solution.

In LOGOSoft  there are just below a block a littele gray squaire with a "+" in it.

Click on it and you get a "Reference" block.

There you can connect references on the same way you connect normal connctions.

In some reference block there is a litlle "+" on the right site of the reference value, there you can change the time bas ( sec, minutes, hour)