Change found text in special textfiles

I have to look for e.g. <FontName type="CString">1LS-Arial</FontName>
in a file. If it is found then change the text in <FontName
type="CString">1LS-OCR-B-10 BT</FontName>
The files are in a folder called Approved and in that folder are
several subfolders with the files to be changed.
The folder Approved and all subfolders are the originals and must stay
original!!

If a file is changed it must be placed in a folder called Corrected and
in the subfolder with the same name as the original subfolder.

If a file not have to be change than also must the file be written to
the folder Corrected in the subfolder with the same name as the
original subfolder.

As a prove of the change I want a textfile with a text like "Filename
FFF.TXT have been changed" if the file is been modified.

Can anyone help me?