Modify product detail viewer

[neibaft]

Hi,
First sorry my English is very limited.
I want to change the viewer productdetail to have arrows to move from one photo to another.
In my product detail page I have several pictures, and when I click on it opens in the viewer and since, I would have arrows to move from one photo to another without closing each time the viewer . I looked in the file default_images.php but I do not know how.
Thank you for your response