I have a container field which contains a reference to a file on the hard disk. I have written a simple script using a custom dialog which will allow me to rename the file on the disk. I would now like to update the container field to point to the renamed file. Is it possible to do this without going through the insert file dialog?

You can write the refernce into the container field with a normal "Set Field" command (Set Field[ <containerfield>; "image:<filespec>] ), from a script or from a Replace command.

Thus, if you can calculate the new name from the old, no problem. Otherwise, you could build a reference table (old name to new name) and use it to get the new name when running a script.