how can i check if a cfimage resize image file is available for display?

I have a coldfusion upload script that is called from a flex application. It deals with large image files (5mb +) and resizes them into 3 smaller sizes for different uses in the flex application.

The upload script containing the resize commands finishes executing and returns a successful result to the flex application, but when the application tries to load the resized images they are not available at that time. They also do not show up on a file system browser until about 20 seconds after the upload script has finished (after which the application displays them correctly as well).

Is there a way to stop an upload script returning until the resized file has been written to the filesystem and thus available to the calling flex application?