Random MIDI pitch notes seem to be quite difficult to generate in the Logic Environment. I made a simple solution using a Max patch, which you can download here or as an OS X standalone app here.
This technique could be useful for triggering multi-sample drum hits of the same type for more variety in drum sequencing.
The Max patch is very straightforward. There is a Trigger Pitch parameter, and if that trigger pitch is detected on the input MIDI device and channel, then the Max patch will generate a random note that is between the trigger pitch and X number of semitones above the trigger pitch. X is equal to the Note Range parameter.
To use the Max patch, first set up an External MIDI Track in Logic. Create some MIDI data on that External MIDI Track using the pitch that should trigger the random notes. Route the output of the MIDI track to a virtual path and channel, as shown below. This will be the virtual path going from Logic to the Max patch.
Go to the Logic Environment, and go to the Clicks and Ports layer. Disconnect the Sum port from the Physical Input object. Consider the virtual path that you wish to use to go from the Max patch to Logic. Connect this path to the Monitor object.
Set up the Max patch using the Trigger Pitch, Pitch Range, Input device (i.e. from Logic to the Max Patch) and output device (i.e. from the Max patch to Logic).