Sorting Memberlist by Last Name

[jpapadpapa]

I need to find a way to:

1. List member last names on the memberlist
2. Put the last name category first in the memberlist, rather than the username first
3. Sort the memberlist alphabetically by members' last names

I have added last names as a custom profile field (field20), but if I add custom profile fields on the memberlist via the CP, then they all show up and I don't want everything there...just last names (and possibly first, as well).

I also found the following thread, which I thought might be helpful. But, I changed the code (as best I could, since this question was asked of an older version), and it did not seem to do anything.

https://vborg.vbsupport.ru/showthread.php?t=67922

Thanks in advance for any help you can give me!

--------------- Added [DATE]1206029781[/DATE] at [TIME]1206029781[/TIME] ---------------

I just read the link within the link I sent that gives me the impression that I can't put just the last name at the front of the list, since I have more than one custom variable.

Any other help would be appreciated.