I've given it some thought... let me try explain some more.
I'm using midi input to control the VST...
Let's say I'm recording the midi commands for the Virtual Guitar and I programme a few changes to the strumming type during the course of my recording.
If I want to continue from where I stopped recording, the VST doesn't know of all the previous midi commands I've input and thus it will be out of sync or play the wrong strumming when I drop in at a bar at the end of that already recorded.
At the moment I have to listen from the start of the track to allow for the VST to pick up on the input I've given it and then I just start the recording as it nears the end of what has already been programmed. This is painful if the song is long because I'm listening through it just for the sake of all the commands being picked up.
I'm wanting to instruct it to process all the commands before that point in time and when I start the playback/recording it's a perfect representation of what it would sound like at that point as if I'd listened all the way from the beginning.