I am editing a book for publication and I want to use Excel as an aid to
compiling the index. I need a way of concatenating the page numbers, which
will
be stored as text values in contiguous ranges of cells that are defined by
changes in a text variable. The concatenated values also need to be separated
by
commas.

Thus, if this is the input:

row0 Col A Col B
row1 antelope 21
row2 antelope 22-3
row3 antelope 25
row4 bears 19
row5 bison 31
row6 bison 33
row7 Colorado 14
row8 Colorado 17

the desired output would be:

row0 Col X Col Y
row1 antelopes 21, 22-3, 25
row2 bears 19
row3 bison 31,33
row4 Colorado 14, 17

(Alternatively the output could be on rows 1, 4, 5, 7 etc; or on rows 3, 4, 6,
8
etc; or anywhere else convenient).

This is similar to the query titled "At each change in data apply
formula", posted by "Shon" on December 11th, 2009, but I'm not
sure that it is quite the same. I would appreciate any suggestions for how to
approach this.