increment a value from one GET to another GET

1. I'm doing a GET which returns a variable number
2. then I am doing a POST
3. then I am trying to run the same GET to see if the value from step one has incremented by 1

How do i do this? The number is never the same in step 1.

I want to be able to assert that the value in step3 = the value in step1 +1.

Do this make sense?