File uploaded to website for processing - determine whether processing has finished

[jmorr]

I have a script that uploads a file to a website for processing. The processing can take anything from 1 to maybe 5 minutes. When the file is ready for download a dialog box appears in the browser, but it doesn't seem to be a window as such and is not identifiable via Window Spy. Is there any other way to check whether the dialog box has appeared, e.g. by grabbing the colour at a given screen position?

[boiler]

Yes, like you described using PixelGetColor, or you can use ImageSearch to look for a section of the dialog box that you save as a reference image.