Digital Performer has a feature that can limit , expand and compress the velocity of note values en mass over time.
Go to Region/Change velocity.
In the top menu there are a few different option available.
Set. This option sets selected notes to a specific velocity.
Add. This allows you to add a set amount of velocity values to a selection of MIDI notes.
Scale. This option uses a percentage value to scale a MIDI note selection Limit. This option allows you to limit note velocities by a specific range.
Compress / Expand. This feature is similar to to an audio compressor / expander in that it will attenuate or turn up velocities based on its parameter settings.
Smooth. This automates smooth velocity changes along a set curve.