Movie clip conundrums

hi all, i have a couple of questions about scrollable movieclips that are loaded into a holder via attachMovie.

i have several buttons which load several different sets of thumbnail images into a holder mc called ‘thumbholder’. once the thumbnail images are loaded into ‘thumbholder’, they can be scrolled up or down via another pair of buttons.

you can see the site so far at http://www.belindagrayphotography.com/test/weddings5.html
(note, so far only the green and blue buttons in the upper left are active)
the fla file is at http://www.belindagrayphotography.com/test/weddings5.fla

the first problem is, if i scroll down the first set of thumbs, then click the blue button to load the second set of thumbs, the second set of thumbs is loaded at the same y position as the first set. is there a way to edit the scripts (loadThumb1 for example) so that it clears the contents of ‘thumbholder’ and returns ‘thumbholder’ to its original position?

my second conundrum is: some of the sets of thumbnails are longer than others. is there a way to edit the script on ‘thumbholder’ so that the scrolling limits are flexible, based on the height of the thumbnails movie clip?

any suggestions, much appreciated.
cheers,
macron.