Assigning variable to chdir of output

What I am trying to do is to have an index.html that opens a generic loader.html (for images), with a different input directory, dependant on which link was activated in the index.html. I have separate loader files (up to 10) for each subdirectory, but the shear quanity is overwhelming me and I need to be able to set variables to do the job. (I will have 200+ dir. w/ up to 200 generic named images each).