Thanks for the suggestion. It seems VPWL_FILE is the way to go, but it is next to impossible to have the high and low side synchronised so they don't short out the two MOSFETs. Do you know what I mean?
I wish I could think of a single voltage source solution to achieve this. I need to go from 45kHz to 85kHz while measuring the current through the S-pin of the lower side MOSFET using a current sensing resistor.
The 100GOhms resistor is going to be replaced with a tuned circuit, that's why this configuration is important.