que bueno. mira ahora dentro de tu boton lo mas elegante seria hacerlo asi:
Código:
import flash.net.FileReferenceList;
var allTypes:Array = new Array();
var imageTypes:Object = new Object();
imageTypes.description = "Images (*.JPG;*.JPEG;*.JPE;*.GIF;*.PNG;)";
imageTypes.extension = "*.jpg; *.jpeg; *.jpe; *.gif; *.png;";
allTypes.push(imageTypes);
//----------------------------------------------------------------
//----------------------------------------------------------------
var textTypes:Object = new Object();
textTypes.description = "Text Files (*.TXT;*.RTF;)";
textTypes.extension = "*.txt; *.rtf";
allTypes.push(textTypes);
var fileRef:FileReferenceList = new FileReferenceList();
//--------------------------------------------------------------
//--------------------------------------------------------------
boton.onRelease = function() {
fileRef.browse(allTypes);
};
como ves dentro de tu boton solo usas el metodo
browse() que sirve para abrir tu caja de dialogo.