<Batch> How to find a line in file and add few lines under it?

I'm trying to find a line

"<!-- here comes the new post -->" 

in an HTML file and add some lines that wi开发者_运维技巧ll contain some vars and special characters like <>#"" below it, without replacing the lines that are already below, because the line will be always in the middle of the file.

--David

You should read Remove multi-line strings from a text file using a batch script.
If you can remove lines you should be also be able to insert lines.