I have exactly the same problem as described by user he1ium at Mar 17, 2010
Please mikrotik guys could you add password option at CLI command /system upgrade upgrade-package-source in next RouterOS release?
otherwise it is impossible to make a template .rsc config for multiple routers with auto upgrade option

Ok I have finally given up on this. When executing the /system upgrade upgrade-package-source cmd, it will prompt you for password

[admin@Mikrotik] > /system upgrade upgrade-package-source add address=1.1.1.1 user=mtupdate
password: <- THIS IS THE PART I AM HAVING TROUBLES SCRIPTING BELOW AND THERE IS NO SET PASSWORD OPTION

Here is the issue. There is no cmd to add/edit/anything the password during or after. This makes scripting the password impossible so far. You can only edit the name and the source. If you copy and paste -

/system upgrade upgrade-package-source add address=1.1.1.1 user=mtupdate
p4$$w0RD

into the terminal, this works fine. But put that same code into /system script and it does not work. Anyone have any ideas?