Beginner's Problems?

Hi All, I’m new to Flash, and am having trouble simply getting my images to tween. I’m trying to shape tween between a closed curtain image and an open curtain image, with two other images in between. In other words, four drawings, spaced about 20 frames from each other. The green tween arrow appears when I click on ‘Shape’ in the drop-down menu, but although the movie runs, there are no transitions between each drawing, so the image just jumps from one to the next. :frowning:

I have made sure to “break” each image, as I know that they won’t tween otherwise.

Hope this is clear enough to understand. Perhaps I’m expecting Flash to do something too complicated? I don’t know actionscript, so am trying to do it automatically.
:h:

Any helpful advice would be much appreciated. I’ve read all the Flash info in the manual and online, and there’s nothing that talks about troubleshooting tweening.