Correct Place to Open Chordpro for a Song

Hi - new to scripting in GP. Where is the right place/approach to have GP open ChordPro Window (via ShowChordProWindow(true)) when I switch to particular songs in my setlist? e.g. I may have a 40 song list, and maybe 6 or 8 of those songs I want it to open ChordPro on when I select them.

I was hoping the “song Script Editor” would be the right place, but it will not accept the “On Song(oldSongIndex : integer, newSongIndex : integer)” handler saying it is allowed in GIG Script only?

In the Gig Script you can use the OnSong callback and react on the the song number

Maybe I don’t understand, but don’t the song numbers change as I move them around in a set list or put them in a different set list?

var CurrentSong : String

on Song (old:integer, new:integer)
 CurrentSong = GetCurrentSongName()
 if CurrentSong == "Us and Them" or
    CurrentSong == "Money" or
    CurrentSong == "Comfortably Numb" or
    CurrentSong == "Have a Cigar" or
    CurrentSong == "Time" then