Allison is correct. You usually cannot edit data in a Data Access Page that you export from a form -- but you often can tweak the DAP properties to make it updatable. Sometimes all it takes is setting the Allow Edits property or the Unique Table property.
As for your specific case where you want to execute
VB code in a DAP -- you can't do that. You'll find that Access exports your
VB code as comments. If you understand VBScript, you can usually rewrite your code to perform the same function.
John Viescas, author
"Microsoft Office Access 2003 Inside Out"
"Running Microsoft Access 2000"
"SQL Queries for Mere Mortals"