I'm working on a problem involving nonlinear vibration, and, while the structural scenario creation app provides procedures that can simulate vibration like frequency, modal dynamic, and harmonic response, it's stated for those that they work using a linear assumption. I read somewhere that I can try to work this problem using the implicit or explicit dynamic procedures, and I'm trying to work that out, but now my problem is that I'm trying to apply a time varying load, I'm trying to apply a sine-sweep excitation but all that's available to me is a constant amplitude force. So my question is how can I apply a time varying load?