You know you can easily do this with the random button of volfx
(at the bottom of the window).
You can also set the amount
of randomness (5 by default).
This way you can easily set a range of minimum/maximum values by first drawing the average value(s) you want to wander around.
Also clicking multiple times on the random button will slowly increase the randomness.
Be sure to check the "notes only" button to enter random values only in the rows where notes are triggered (most of the time you don't want to randomly modify the volume after the note is triggered as it can sound pretty bad).
If this was implemented in ompt, it would be better to at least be able to control the amount of randomness or alternatively to be able to set a maximum and a minimum value.
Pure random values is not very musical in most cases : you don't want to have extreme panning values or 0 volume, etc... you need a bit more control don't you think ?