Once I call dos, how do I add new lines to execute?

I've tried these methods... and nada

dos('CMD.exe') 
dos('nslookup ')
dos('set type=MX') 
dos('google.com') 

command1 = 'nslookup';
command2 = 'set type=MX';
command3 = 'google.com';
system(command1,command2,command3)
dos(command1,command2,command3)