I can't believe it. Found "PATHMAN.EXE" on the Resource Kit. I've also taken out the comments as my last post got messed up.

; Environment modification
$v = INSTR("%PATH%",U:\")
If $v > 0
Goto PathSet
EndIf
If @INWIN = 1
Shell "PATHMAN /AS U:\"
EndIf
If @INWIN = 2
Shell "WINSET PATH=%PATH%;U:\"
EndIf
:PathSet