Just as with Program Change messages you can enter MIDI Volume messages in the Inspector for individual Parts or in the Track Columns for Tracks, for example to get a basic mix at the beginning and to introduce volume changes at different positions in the Song.
When Cubase VST plays back this Part, the instrument will receive a MIDI Volume message to set its Volume to a value of 115.
• If you enter a Volume Change for the Track, this Volume Change will be sent out at the beginning of the first Part only.
This is to avoid having a lot of MIDI data sent out at the beginning of each Part.