Best way to truncate a string on Activities Panel

I need to add a description field to the Activities sub-panel. So this is the Notes description, Calls description and Task description but if I add this field as it returns from the DB, it can be very long so I wanted to truncate it down to 100 characters. I found this reference
but it truncated my description on the detail view also. I cannot believe how difficult this is!! It would be so easy in the DB query.
I found that it calls get_subpanel_data but I have been able to find where that function is to extend it.
Any help would be greatly appreciated.