PSP will do this for you.
(1) Set PSS with input port at the power level that you want
(2) Set PSP with input and output port that you want to check, set the harmonic at input and output at harmonic = 1 (or specified harmonic tone that you would check the S-parameter), set the single sweep frequency at the input frequency (relative 0Hz or Absolute fundamental freq.)
(3) sweep the PSS frequency can cover the frequency that you want to check.
Under some condition, you can keep the PSS frequency and sweep a (small) frequency range under PSP. and still get accuracte results. (but much faster)
Simon