You can use menuscript to add an action (running your journal) after the file open command is used. Consult the help file Automation -> MenuScript user's guide, and Automation -> NXOpen Programmer's guide -> Execution methods for details of how to set it up.
While nothing special is needed to create or run a MenuScript, what you're doing is executing some other application and depending on what that might be, you may need a license for that.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA