Simple "LoadMovie into Container" question

Hey guys, hope everyone is doing well…
This is really simple to answer, I’m sure, I just can’t find any quick and easy answers for this. Also, Im not sure about the terminology…

I have a main flash movie, with a square mc called “container” 150px x 150px

When this loads, i just want another external .swf file (the same dimensions, called “block”) to load into “container” mc, without the need to click on a button first…

Thats it…nothing else fancy…

This is the code I have on “container” :

onClipEvent (load) {
  container.loadMovie("block.swf");
 }

Can anyone help?