Subtracting Two Real time Values to get the result


I am stuck with this expression to subtract 2 realtime different values to get the result in a numerical label.

I have HPP Discharge readings value and HPP Suction readings value, I have to find the differential pressure for these real time values.

Can anyone help!! I am currently using V7.5

Basics like this and more are covered well in Inductive University materials. In this case, you’re looking for an expression binding: