Append permissions to all subfolders

Hi,

I've got a large number of files/folders/subfolders. Many of the folder have their own unique NTFS permissions, either in combination with inheritance, or exclusive. 

I now need to give a certain group full permissions to all files/folders/subfolders, but i cant screw with the existing permissions. Meaning, if i assign it to a top level folder and push it down, it will overwrite the folders exciting permissions. I basically need for all NTFS permissions to remain intact, and at the same time, add/append this new group to all files/folders.

Is this possible?