Kontakt Script to play_note() with keyswitch

I need a script to retrigger a held note when a keyswitch is depressed to change the group. I'm surprised this isn't a standard function to allow changing articulations with sustained notes, unless it's been added since Kontakt 5.

The application is for guitar glissandos along a single string. The glissando samples are in separate groups with the attack removed to blend seamlessly with the initiated note. The glissando groups are currently activated by Release Trigger while their group start keyswitch is activated. This works perfectly to blend the samples together, but is awkward to play and there is no easy way to stop the glissando sample because releasing either the note or the keyswitch does not cancel release triggers.

Can someone provide a short script to retrigger a held note to play a new sample when a keyswitch is depressed? It needs to play a new sample from the keyswitch assigned group while simultaneously ending the sample already playing prior to pressing the keyswitch. And releasing the held note needs to end the new sample.