Custom pagers in a block referring to a specific views with thumbnails

Issue Summary

Hello,
I am using the latest versions of drupal, views and tokens. Somehow, I am not suceeding in creating a pager that lets me have a next and previous photo. I have a view that generates a thumbnail gallery of multiple images of the same image field in one node. Then, for each thumbnail, I have a custom field in which I get the URL to the enlarged image written in PHP, so that the enlarged image occupies the block in which were the thumbnails.
I would like a pager living in another block to browse previous and next enlarged image, according to the thumbnail gallery. When I try to create such a custom pager, it doesn't even show io in the block (I chose the region in which it should appear in the Blocks page).
If I can help by posting any other specific information, please tell me so.
Thank you for any help.
Thank you for any help.