|Razor's suggestion might be fair game for my comments.|
The trick is to get "start ." to reflect back into the batchscript.
I do not know how to do this, but that is my own limitation.
batch-script does not support a window/gui browsing facility, although vbscript does, ( i think ). I think a batch-driven browser is not too hard to write, maybe, but i haven't made any serious effort yet. it would be a BIG script!
windows communications between GUI and batch/cmd-prompt is very very limited, and often requires "externals" such as reg.exe, debug, vbscript, etc. or other "third party" (read: *nix) utilities. Often you need to use a "squibfile" (my workd for short ascii-text communications file)
My assumption is you want to let the user "fish around" in the file system to find 1) the text file, then 2) the directory. There might be better approach, such as making textfilename as constant and offering all instances of that, (found on filesystem) and making directory as a subset of the filesystem.
sorry this long blather not much help, but your problem is genuine and possibly addressable (even using batch only).
let me know what you think, and my recommendation is to go the vbscrip route. I can try to hep with that but not good at that either!!