Problem adding transition on XML Slidedeshow/Photogallery

okay. Darylmeter posted this link as an example for xml transition.
http://blog.reintroducing.com/index.php/27/07/2005/42

now im trying to merge this idea into the xml photogallery/slideshow.
problem is that the example transition has 3 different movieclip loading
individually their xml pic . while the xml slideshow/photogallery has one blank movieclip which is named ‘picture’.

the transition uses
movieclip.swapDepths(_root.getNextHighestDepth());
every time the button is pushed, covering the previous movie with
another movie to create a nice mask/transition.

problem is how can i make 2 blank movieclips exchanges depth at the same time while they are loading xml images so their masking/transition is nicely done covering any previous pic that is loaded. the xml slideshow/photogallery has only one movieclip that loads the xml pic, which is really giving me a difficult time as a beginner/novice.

movieclip(mask_mc & load_xml_photo_mc)
|
exchange depth
|
movieclip2(mask_mc & load_xml_photo_mc)

hope you guys got my idea…