Just add another message in the invoice. There you set it as an Special function and you have to cusomize it as an ATM-Message, when saving the document.
Now you have to develop a program, which does select the NAST-Entries, you want to print and afterwards ( Selecting is done ) you have to call the FuBa wmfc_message_single in a loop.
There you go, all your papers will be printed, without any clicking
I know, it is not done, by just selecting the NAST-Entries, but it doesn't sound that difficult. You have to develop a bit between, to make sure, all stuff is in stock and the other conditions are matched.
~Florian