Scrolling thumbs gallery offset

hi guys,

i’m currently re-using a code snippet of xml gallery with scrolling thumbs, but i got a problem :
my mask is stagewidth and my pictures holder width depend of thumbs numbers,
sometimes after resizing windows browser, while scrolling to the browser sides limit i cannot see the end of the last pic or the start of the first pic,
how to fix that ?

tha’ts part of a bigger project, but i’ve isolated the bug in this source :
http://missjohanna.free.fr/scrollbug.zip

the fix i would like :
-seeing the whole first pic and whole last pic when scrolling to the border left and right
-placing the first pic at x:70 at start, and enter fullscreen

i’ve tried many thing, but unfortunately, due to my poor as3 knowledge i cannot figure out how to fix that…

if someone may have a look on this ,
that’s only a 2 mn fix for a skilled as3 programmer,
but for me a headache;(

thanks a lot

dan