Lease help me, I'd need to create XForms binding-exception with XHTML page

Question

Hello,
is anyone here who could help me?
I've spent plenty of hours by searching the correct and suitable way for creating a binding exception in XForms, but I did not succeed...
My situation is: I've got an XHTML page with XForms and XML (input) file, which describes this page. Whenewer I change the input data in the XML file (for example if there are tags <person> and ....</person> if I change it to <peson1> and ...</person1>) after saving the changes and refreshing the page, the XForms are changed (for example some text fields are missing or they've got white background instead red one, which there was before et cetera). {I hope it is clear till now.....}
My task is: to create a xforms-binding-expression event, which will display an error message (for example: FILE HAVE BEEN CHANGED, CAN NOT DISPLAY THE PAGE PROPERLY) to the user.
i've found some stuff, how to create such message, but i need to know the exact order of commands to make it work, where to insert them, the structure etc, so I can comprehend your advices...
The XHTML file contains of several blocks - bind, model, submission, instance etc - and I do not actually know, where to insert such lines (with message)...I think I should make some bindings with the page loading, but I've got no idea how to get it done, however there are very few sites with such stuff on the internet. I hope this task is no big deal for you gyus, THANK YOU A LOT IN ADVANCE

Answer 1

Thank you very much. I am new to this, and but am not exactly sure how to run a script. Can it be run as a one-off using the editor or console like AppleScript and hitting the green arrow, or do I need to put this into a file and save it to the scripts folder first?
Also, a related question: some of my scans are full page Letter already and I need to reduce them (scale them) so that they print with a margin because the pages need to be hole punched.
Can you help me incorporate into this code something that says, if the trim box  > 8 x 10 then scale the page by x percent or by whatever allowable means Acrobat will do it? This way, those pages will be permanently scaled smaller. I cannot just print them scaled smaller, because then all the scans will be printed smaller, and I only need the largest ones reduced in size.
Thanks so much.