Scrolling Thumbnail Panel

1

My scrolling thumbnail panel work great but I want to ad some extra functionality. I have two arrows above the panel. One for left and one for right.
Once the panel gets all the way to the left I want the left arrows alpha value to be set at 0 and once it begins to scroll right it needs to be visible again.

here is my attempt. Only the left arrows alpha is at 0 since beginning xPos is 0.


mouseX = _xmouse;
mouseY = _ymouse;
menuX = menu._x;
// -----------
function gotoURL(movieNum) {
    getURL("javascript:flashURL("+movieNum+");");
}
// ------------
if (mouseX>314) {
    diff = (mouseX-314)/40;
}
if (mouseX<313) {
    diff = (313-mouseX)/40;
}
if (mouseX<=313 && mouseX>=10 && mouseY>=100 && mouseY<=575 && menuX<=0) {
    setProperty("menu", _x, menuX+diff);
}
if (mouseX>=314 && mouseX<=617 && mouseY>=100 && mouseY<=575 && menuX>=-627) {
    setProperty("menu", _x, menuX-diff);
}
if (menu._x>=0) {
    menu._x = 0;
} else if (menu._x<=-627) {
    menu._x = -627;
}
// ---------
gotoAndPlay(1);
// ----------
// Hide Arrows
menu.onEnterFrame = function() {
    if (menuX<=0) {
        lArrow._alpha = 0;
    } else if (menuX>=625) {
        rArrow._alpha = 0;
    }
};
// show arrows
menu.onEnterFrame = function() {
    if (menuX>=1) {
        lArrow._alpha = 100;
    } else if (menuX<=625) {
        rArrow._alpha = 100;
    }
};
// -----------
// see all styles button 
b5.onPress = function() {
    _root.gotoURL(5);
};