How to detect not changing variable

Hello Experts , 

I want function in S7300 that detect variable is not changing (fixed) with definite time then I can trigger to stop logic output . 

Is there function can do that ? 

Thanks 

 Translate the following segment and you will have what you seek.

I appreciate your reply but as you know for analogue values there is small change in the value even if the real value not changed so how to control the amount of variance that detect the error . 

Thanks 

mopS04

hi,

no block, but easy to program:

just extend the second network with an SUB-block and you will get the rate of change between two cycles,

regards,

 Too Thanks 

mopS04

hi,

no block, but easy to program:

just extend the second network with an SUB-block and you will get the rate of change between two cycles,

regards,

 I tried this method but the problem when there is no change in the variable , the rate of change keep the last saved value but I need it to be zero when the variable value became fixed