I also had that problem. Picking the UID is a solution, but the UID can change by deleting/adding objects. My method was the following:
I created a global variable(counter) and a private variable ID for the object. Now I add to the foreach action: add 1 to global('counter') and set object('ID') to global('counter').
So it creates the object, and increases the counter everytime when the sprite is created and assigns the number to the ID.
Short: every object has its own number in its private variable <img src="smileys/smiley2.gif" border="0" align="middle" />
You only have to put on the conditions: object('ID') = 2. If you want to make something with the 2nd object.
It was a little hard for me, to explain it in english. So if you don't understand anything, just reply.