how to plot a spectogram changing the time axis by the input frequency axis of the excitation signal instead?

Hi I want to plot a spectrogram of a measured Signal, the Response of a System to a sweep Signal in a certain frequency range. I would like to Analyse the spectra of the Signal at frequency Points and not at time Points, as what I am trying to anlyse is, if when applying a Signal with a certain frequency to the System, I obtain spectra at multiples of that frequency. That is, I would like to transform the time axis to a frequency axis instead.

I would be very grateful if somebody could help me...