How can I create a horizontal list of text values from a vertical list. For
instance:

Part 1 abc
Part 1 def
Part 1 ghi
Part 2 abc
Part 3 def
Part 3 jkl

I would like the above data to look like this (or something similar):

Part 1 abc, def, ghi
Part 2 def
Part 3 def, jkl