@iantresman, my bigger version shows the same options but it’s bigger. 
Here it is, I have shared it in a Tools folder where you should see my bigger mediatools.exe (2/3/2010 / 1.79 MB).
Also, here are two demos that show you how you can copy the whole ISRC list result from this program for an all at once submission.
In my examples, I copy from a website but it’s the same approach, just copy all then paste all in @kepstin’s magicisrc’s first input (if your ISRC list starts at track 1).
Temporary bookmarklet that enables paste all: javascript:var mbid=location.pathname.match(/^\/release\/([a-f0-9]{8}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{12})/);if(mbid)void(open("https://rawgit.com/jesus2099/kepstin_magicisrc/%25231-support-pasting-multiple-isrcs/index.html?mbid="+mbid[1])); (create an entry with this code as URL in your favourites/bookmarks toolbar, then click it when you’re on your release).
This is completely subject to change because it’s in the middle of a work in progress. 
At least it is sure it will change, so your bookmarklet will need to change sometime.
Important. Remember to always go back to your release edit history after submitting an ISRC set to write in the edit note to which release you added them (paste release URL) and from where you got them (CD with mediatools.exe, CUE sheet from who knows where, minc rip, etc.)
Because otherwise, this no text edit will appear in all recordings edit histories and they are quite difficult to trust or are only hardly helpful for any post review/diagnose of future merge problems, etc.