Are you looking at also doing a US/ Canada specific phone number validation/ formatting?
Altough the 10 digit number is a phone number, I am just looking for a spry text validation with numeric entries only, with no spaces and a min and max of 10 characters.
Then, you can do it with behaviors in DW. With your 'input' for number field selected either in code or design view, go to 'Behaviors' panel (if it is now shown already, click Window > Behaviors to show it).
Click the 'Plus' callout button > Validate Form.
Choose the field that you're validating (in your case, id_number). Accept 'Number from' 10 to 10 (min and max 10). Hit OK.
Btw, just so you know, Spry is no longer being officially supported by Adobe. http://blogs.adobe.com/dreamweaver/2012/08/update-on-adobe-spry-framework-availability.htm l
Start moving to/ learning jQuery.