Object from flash to unity

I'm trying to send an object from flash to my unity swf export that I'm loading, everything works fine, even if I send it back to flash I can read it's properties, but seems like I can't do it on my c#.

Here's what I'm sending:

var myObj:Object = { _x:xPos, _y:yPos }; unitLoader.unityContent.sendMessage("Cube", "SetPosition", myObj );

And here's how I'm trying to access it:

void SetPosition(object o) { float _x = o._x; float _y = o._y;

}

But Unity won't even let me compile this, saying that "o" has no _x or _y property. Can anyone help me with that? Thanks