ie: 
 
Allowed_Users = Z !* 
 
so if you want users to be able to access that FTP you use: 
site change [username] flags +Z 
 
keep in mind that flags can be used for whatever you want.  Besides the M, V, F, f, and L flags, which have pre-defined meanings, every other letter/number is definable by user (you).   
 
in the above example, you have defined the Z flag as a flag required to log into your FTP.  it's as simple as that.
		 
		
		
		
		
		
		
		
	 |