Automatic add new users to list "task for"

Hello all,

Is there any option how to automatic add user in task lists depending on AD group of useres?

For example:

Some document is send via workflow to sign (task for to check it) to some group of users. After that i would like to automatic add a new user (for example when an new employee appears in user group ) to sign this. But i dont want to start a workflow again. I have no idea how to automatic add (now I am able to add a new user only manual.

Has anyone solved it yet?. Is there any options how to do it? Script? . 

Thank you some much.