How one xml file call another modified xml file like without a user intervention ?.

["M. Amin" <am...@imkenberg.net>]

Hi all,
 I have a small logic problem.
In my xml file for example "user.xml" the user enters his personal information which are sent 
directly to another xml file for example "check-user.xml" which checks that all of the mandatory
user's attributes are entered by the user. If one of the attributes is missed, "check-user.xml" must call back "user.xml"
with a error message indicating missed attributes for the user.
My question is how one xml file like "check-user.xml" (which will be hidden for the user) call 
another modified xml file like "user.xml" without a user intervention ?.
or How can i handle this task in xml ?

M. Amin