No, it is not possible to put Actionscript 2.0 code in an Actionscript 3.0 code file. The Actionscript virtual machine that runs Actionscript 3.0 code is completely different from the Actionscript 1.0 and 2.0 virtual machine. The only way to include Actionscript 2.0 code in an Actionscript 3.0 project would be to have the Actionscript 3.0 Flash file load an external Actionscript 2.0 Flash file.