Derivative with respect to parametric sweep Variable

Hello,

I am having troubles to get a derivative of a Variable which does not directly depend on a sweep parameter.
For Example:

Variable:
A1=intop1(rmm.Az)/Surface

Now I define a sweep parameter called "stage" to have a parametrized Geometry and in every Solution A1 differs. So a plot of "A1" with respect to "stage" is not constant.

What i now want to do is to get the derivative of "A1" with respect to "stage". If I define it as

d(A1, stage)

the result is zero.

Is there a way i can define that derivative?


Thanks in advance