MACROMEDIA FLASH 8-LEARNING ACTIONSCRIPT 2.0 IN FLASH Manual page 300

To select a different frame for the classes to load into a SWF file:
1. Select File > Publish Settings.
2.
Select the Flash tab, and click the Settings button.
3.
In the Export Frame for Classes text box, type the number of a new frame to determine
when to load the classes.
4.
Click OK.
You cannot use any classes until the playhead reaches the frame you choose to load them into.
For example, version 2 components require classes for their functionality, so you must load
components after the Export frame for ActionScript 2.0 classes. If you export for Frame 3,
you cannot use anything from those classes until the playhead reaches Frame 3 and loads
the data.
If you want to preload a file that uses classes, such as version 2 component classes, you must
preload the components in the SWF file. To accomplish this, you must set your components
to export for a different frame in the SWF file. By default, the UI components export in
Frame 1 of the SWF file, so make sure that you deselect Export in First Frame from the
component's Linkage dialog box.
If components do not load on the first frame, you can create a custom progress bar for the first
frame of the SWF file. Do not reference any components in your ActionScript or include any
components on the Stage until you load the classes for the frame you specified in the Export
Frame for Classes text box.
You must export components after the ActionScript classes that they use.
300 Classes