Those instructions were wrong and have been fixed. Here's the usage for
RUNAS [ [/noprofile | /profile] [/env] [/savecred | /netonly] ]
RUNAS [ [/noprofile | /profile] [/env] [/savecred] ]
/smartcard [/user:<UserName>] program
RUNAS /trustlevel:<TrustLevel> program
Notice that in all three variations, you can specify only a program to be run, nothing else. They mean it: You cannot specify any arguments to the program as separate words. Any arguments must be embedded into the "program" string with surrounding quotes.
Also not made clear is that
runas will not pass the current directories; it always starts in
C:\Windows\System32. So any program you specify must either be in a
PATH directory or given as a full path. You cannot use a relative path. And of course, any ACLs on that executable or the directories on its path must allow access by the user you'd like to run it as.
The good news is that
runas will accept a
.cmd file as a "program".
As a practical matter, what this means is that to do what you want, you'll probably want to create a
.cmd file in a directory both users can access, then pass the full path. For example:
runas /u:Fred "C:\Users\Public\foo.cmd"
The final wrinkle is that
runas can start a program as another user, but it can't elevate. There's no way to cause it to generate the UAC prompt. If you'd like to run something "as administrator" using
runas, you'll have to enable the builtin Administrator account, which always runs elevated anyway, and specify that user name.
If that's not going to work for you and you need a generalized ability to pass arguments and/or current directories or if you need to run something elevated as something other than Administrator, you'll need a genuine
su, like this one.