Triggers a script to run each time you open a window of a database file when no other windows for the file are open.
When the script runs
After the first window of a file is opened.
Modes in which the trigger can be used
OnFirstWindowOpen activates before FileMaker Pro enters a mode.
Originated in
FileMaker Pro 12.0
Although this is typically the first time you open a file, you can also trigger a script this way when you open a window for a hidden file previously opened via a script or relationship.
Related topics 
Setting up script triggers
Setting script triggers for layouts
Setting script triggers for objects