Thanks for the reply.
I'm terrible sorry - having re-read my question in the first post, I see that it is not correct. What I really ment is this:
I want my script to add to a list only the files (i.e., filenames) modified since last time the script was run. I'm thinking I should have a file containing only the time the script was last run, and compare this with the other files in the direcetory. To be a little more precise: I'm developing a program, and I want to sort out those files having been modified since the last time the script was run. This script copies the modified source files to machines on the network, and I want to send only the source files having been modified (or else the machines will waste a lot of time re-compiling files that have not been modified). Any ideas?