Gasper

I have a problem.

I'd like to replace an URL in several .html files in several directories.

The structure is like this:
/dir
/dir1/
html1.html
html2.html
html3.html
/dir2/
somehtml1.html
somehtml2.html
somehtml3.html
.....

I would like to replace an URL with another one in all files and in all directories (dir1, dir2, dir3...). Is this doable?

Please help