Image Gallery Tutorail

I have used the image gallery tutorial that I found here. I have everything working but the scrolling thumbnails. I can get it to work the way it is suppose to but I want to edit it a little bit. Instead of moving left to right at a constant speed, I would like to have the thumbnails jump left or right by 50 px. I am trying to have the thumbnails fill a static frame. So I need the frame to stay still and he thumbnails to move.

I have tried a few different things in the that I found in the forum but I can not get them to move the way I need them too. Below is the code that is part of the original gallery that tells the movie clip to move:

function thumbNailScroller()      
{ // thumbnail code! 
scroll_speed =10; 
tscroller.onEnterFrame         = function()         
{ if ((_root._ymouse>=thumbnail_mc._y) && (_root._ymouse<=thumbnail_mc._y+thumbnail_mc._height)) 
{ if ((_root._xmouse>=(hit_right._x-40))                 && (thumbnail_mc.hitTest(hit_right))) 
{ thumbnail_mc._x  -= scroll_speed;} else                
 if ((_root._xmouse<=40) && (thumbnail_mc.hitTest(hit_left)))                 
{ thumbnail_mc._x += scroll_speed;}} 
{ delete tscroller.onEnterFrame;}

I think that is the part of the code that controls the scrolling of the movie.

Please someone help, I’m really confused. And not very good at this stuff.