Apologies for not making myself clearer!
Let's say I have my concert of 100 patches. Each patch has an external instrument channel strip with its program change send feature enabled. For patch 1 it sends PC 1, for patch 2 it sends PC 2. All is good. Now I need to add a new patch as the second one in the concert. Patch 1 can stay as it is and the new patch 2 now sends PC 2. But the external instrument in the old patch 2 (which is now the third one) needs to be be edited, because it now needs to send PC 3. Patch 4 (which used to be number 3) needs to be edited because now it needs to send PC 4 and so on. So I have to go through the whole concert, scroll to the right in the mixer, click the channel strip, click on MIDI output, edit the program change number and repeat 98 times.
As there is no way to bind the outgoing program change number of an external instrument channel strip to the incoming one of the patch, I thought about using Scripter for that.