ActionScript Code:

var loader:Loader = new Loader();
loader.load(new URLRequest("AS2file.swf"));
addChild(loader);

var receiveSwf_lc:LocalConnection = new LocalConnection();

receiveSwf_lc.client = this;

function showGallery1(){
    var requestNew:URLRequest = new URLRequest("newAS3.swf");
    var loaderNew:Loader = new Loader()
    loaderNew.load(requestNew);
    holderMC.addChild(loaderNew);
}

//listen.... ("connection name")
receiveSwf_lc.connect("AVM1toAVM2");

ActionScript Code:

var sendSwf_lc:LocalConnection = new LocalConnection();

loadBtn.onRelease=function(){
    //send instruction.... ("connection name", "function name")
    sendSwf_lc.send("AVM1toAVM2", "showGallery1");
}