Let's say I want to emit only 100 particles over a certain amount of time. How can I limit the particle emission to only 100. I don't want to emit 100 at once. I just want the emission to stop as soon as the particle count reaches 100 particles.

Use the birth parameter. If you know how long your simulation will run you can calculate the number of births: no. particles/seconds of sim. In your case it would be just 10 with a 240 frame sim.

Another option is to use the Max # of particles on the popnet node. This will limit the emission to 100 particles but you have still control over the birthing speed.

That's exactly what I was looking for. Thank you very much.