Photo Gallery Help

Ive been trying to get my next button and previous button to work. What im trying to do is:
first 25 thumbnails tween in from right to left then when the next button is pressed the thumbnails on stage fade and slide out to the right and the next 25 thumbnails fade and slide on to stage and so on. When the previous button is pressed the thumbnails on stage fade and slide to the right and if there are any previous thumbnails they fade and slide from the left to the right. This is my next previous button code that ive tried but with no success.

next_previous_mc.next_btn.onPress = function()
{
 if (!_root.largeTab._visible)
 {
  currentTab++;
  makeTab();
var newMC:MovieClip = mcTab.duplicateMovieClip("mcTab_copy" + i, i, {_visible:true});
            newMC.id = begin + i + 1;
            newMC._alpha = 100;
            newMC.stopTween(["_x"],["_alpha"]);
            newMC.endX = mcTab._x + ((i % 5) * (mcTab._width + 20));
            newMC.endY = mcTab._y + (Math.floor(i / 5) * (mcTab._height + 10));
            newMC._x = newMC.endX - 1500;
            newMC._y = newMC.endY;
            newMC.tween(["_x", "_alpha"],[newMC.endX, 0],0.5,"easeOutQuad",i * .1);
            var newMC:MovieClip = mcTab.duplicateMovieClip("mcTab_copy" + i, i, {_visible:true});
            newMC.id = begin + i + 1;
            newMC._alpha = 100;
            newMC.stopTween(["_x"],["_alpha"]);
            newMC.endX = mcTab._x + ((i % 5) * (mcTab._width + 20));
            newMC.endY = mcTab._y + (Math.floor(i / 5) * (mcTab._height + 10));
            newMC._x = newMC.endX - 1500;
            newMC._y = newMC.endY;
            newMC.tween(["_x", "_alpha"],[newMC.endX, 0],0.5,"easeOutQuad",i * .1);
            this._visible = curPic > 1;
            this._parent.next_btn._visible = curPic < totalThumbs;

 }
 else
 {
  if (curPic < totalThumbs)
  {
   curPic++;
   large_mcl.loadClip(online + "images/" + curPic + ".png",_root.largeTab.image_holder);
   this._visible = curPic < totalThumbs;
   this._parent.prev_btn._visible = curPic > 1;
  }
 }
};
next_previous_mc.prev_btn.onPress = function()
{
 if (!_root.largeTab._visible)
 {
  currentTab--;
  makeTab();
 }
 else
 {
  if (curPic > 1)
  {
   curPic--;
   large_mcl.loadClip(online + "images/" + curPic + ".png",_root.largeTab.image_holder);
   this._visible = curPic > 1;
   this._parent.next_btn._visible = curPic < totalThumbs;
var newMC:MovieClip = mcTab.duplicateMovieClip("mcTab_copy" + i, i, {_visible:true});
            newMC.id = begin + i + 1;
            newMC._alpha = 100;
            newMC.stopTween(["_x"],["_alpha"]);
            newMC.endX = mcTab._x + ((i % 5) * (mcTab._width + 20));
            newMC.endY = mcTab._y + (Math.floor(i / 5) * (mcTab._height + 10));
            newMC._x = newMC.endX - 1500;
            newMC._y = newMC.endY;
            newMC.tween(["_x", "_alpha"],[newMC.endX, 0],0.5,"easeOutQuad",i * .1);
            var newMC:MovieClip = mcTab.duplicateMovieClip("mcTab_copy" + i, i, {_visible:true});
            newMC.id = begin + i + 1;
            newMC._alpha = 0;
            newMC.stopTween(["_x"],["_alpha"]);
            newMC.endX = mcTab._x + ((i % 5) * (mcTab._width + 20));
            newMC.endY = mcTab._y + (Math.floor(i / 5) * (mcTab._height + 10));
            newMC._x = newMC.endX 0;
            newMC._y = newMC.endY;
            newMC.tween(["_x", "_alpha"],[newMC.endX, 100],0.5,"easeOutQuad",i * .1);
            this._visible = curPic > 1;
            this._parent.next_btn._visible = curPic < totalThumbs;

  }
 }
};

Sooooo Frustrated with this can ayone please help???