Totally agree with Les, select would be better.
Code:

Use L: /DEL
Select
	Case @USERID = "bdunn"
		Use L: "\\enterprise\WinSchl\Melissa Middle School\Melis101\eclass\18"
	Case @USERID = "SomeoneElse"
		Use L: "\\enterprise\WinSchl\Melissa Middle School\Melis101\eclass\OtherNumberIPresume"
EndSelect

I would review the installation of the program itself. Does it support UNC paths? If I understand well, the userdata is being written to L:.
I would like p.e. that the userdata could be written to a path like
"\\enterprise\WinSchl\Melissa Middle School\Melis101\eclass\%USERNAME%".
No need to do tricks during logon.
IMHO, even a subdirectory in the userdirectory would be much better.