Pitchbend Inverter is a very simple MIDI-only JSFX script that inverts the Pitchbend's effective value: up-shifts become down-shifts of equal amount, as long as the receiving synth has an equal up/down range on both sides (which should be the most common case). It also handles the fact that negative (down) pitchbends are slightly more precise than positive (up) pitchbends (8192 values instead of 8191, because of zero), so it does the proper conversion. Please note that it inverts all pitchbend messages, on any channel. If you want only a specific channel inverted, then please route it accordingly in the host.
One use of this script would be to link the inverted result to a synth parameter that should go the opposite way of the pitchbend. For example, let's say you have a simple sampler that does basic pitchbending by slowing down or speeding up the samples. You want to time-stretch the sample itself, without affecting its pitch, but only its speed. To do that, send the pitchbend to the sampler to have the samples play faster or slower (which also modifies their pitch), and then use a pitch shifter effect, with the amount of shift equal to the inverted pitchbend. Basically, you play the sample faster and then down-pitch it back, or play it slower and then up-pitch it back. So, you just achieved crude (and manual) time-stretching. This is just one example, feel free to use it for anything else.