I would like to take the voltage at a particular node in a transient analysis and use it as the Vhigh value for an inverting schmidt trigger. Does anyone know how to do this?

 

Bob, I don't usually worry about the inverting schmitt trigger when I'm analyzing circuits. I'm typically more concerned about the analog signal going into the schmitt trigger. Assuming that that your output impedance is more than a factor of 10 lower than the input impedance of the schmitt trigger, you should be okay.

Having said that - If you know what schmitt trigger you're using, you might be able to get the spice model from your third party and pull it into ltspice.