Find and add

Hi,

I have a file with multiple lines starting with word 'newuser'. I want to go to the last line starting with 'newuser' and add another line starting with 'newuser' followed by 10 spaces and then words entered by the user. I using the following command but it does not seem to work.

sed '/*\/^newuser/ a\
newuser '$user' $file > $file.new

Thanks.

Moderators, this post is a continuation of sed help again's post #4.