dynamic content of footer base on field

Luffy

Hi everyone, I run xml on bi puplisher on word. I create a footer section by custome code in my body code"

<?template: footer_content?>

            A

<?end template?>

and on footer section I call:

<?call: footer_content?>

 <?end call?>

A is where I want to change dynamic value of filed of student_number.But i don't know how to code content of template footer_content. It always get one value. I try to put <?MA_HOC_SINH?> in A but it is not ok. But it According to my body code, it automatically change value of student_number. So, how to code dynamic content follow field of student_number. Thank you for your time and in advance.