Set the default printer using command shell

I want to set my default printer using a command shell, can it be done?

Yes...

Running "RUNDLL32 PRINTUI.DLL,PrintUIEntry /?" gives you a list of what you can do, and this help you set the default printer:
RUNDLL32 PRINTUI.DLL,PrintUIEntry /y /n "hp psc 1200 series"

See: Usage and examples