Hi, Jerry,
I afraid you misunderstood the documentation of dcl-form-show.
You are right that there's written that return values can be a number, a string, or a list of strings.
But actually, a string is returned by a custom file selection dialog (which is also modal) with single file selection mode and a list of strings (filenames) is returned by a custom file selection dialog in multi file selection mode.
For your case, you have to build a function/command with events - for instance when Ok was pressed - to collect all the data into a variable.
I hope its more clear now.
With regards, Fred