An easy to understand example to make a link-button:
swf_startbutton ($this->gClick, TYPE_PUSHBUTTON);
swf_addButtonRecord (BSDown|BSOver|BSHitTest|BSUp, $this->gButton, $this->gDepth);
swf_onCondition (OverUptoOverDown);
swf_actionGetUrl ($this->gotoUrl, $this->target);
swf_endbutton();
This example is out of a link-object.
gClick is the ObjectId which you need for the swf_placeobject.
gButton is a defined shape which defines the clickarea.
rest is clear i think.
So, I think this is the easiest way making a button.