Basic website photo gallery

This doesn't sound difficult but I have no idea if it's possible or not. I am in the process of creating a website and I want a very basic picture gallery on it. I appreciate there are other ways to do this but the way I would like to do it is to have a web page which simply displays a picture and a next and previous button to change pictures. This much I can do myself. How I ideally want it to work is to have the page automatically display a picture named 001.jpg. When you click the next button it goes to [login to view URL] and so on. All pictures will be named in this format and stored in a single folder on the server. The technical part is that I want the next button to display ONLY if [login to view URL] exists (or [login to view URL] if looking at 002.jpg...or [login to view URL] if looking at 003.jpg...and so on). Alternatively, the next button can stay displayed but only if a script can be created which says if there is no picture with a higher number then go back to 001.jpg. Obviously I would look for similar functionality at the other end with the "previous" button. (i.e. it doesn't display on [login to view URL] or alternatively goes to the highest numbered jpg file). The number of pictures will be constantly changing and the gallery will be administered by someone who is capable of no more than correctly naming the images and uploading them. HTML editing for arrays and things is out. Button graphics etc are not an issue...that much I can do...it's simply a script that I am after!