Do you wish to send each different midi notein to a different event in Max? If so take a note of each midi note number and add them to a [select] or [route] object. Not familiar with the TD8, but in GM all percussion is ‘hardwired’ to channel 10. Usually.

But surely velocity is an ‘unpredictable’ variable, where midinote# isn’t. If, by isolate, you mean extract each momentary velocity and then ‘do something’ with that value, then you have perhaps looked at [maximum]? Try filtering your question down to one or two keywords and using the forum search. Have you built a patch already? Maybe post that here.