[NGUI] Attach a Progress bar to a instantiate object

So in enemy script(instantiate object) i have variable “public UISlider healthSlider”.
How to attach to this variable a existing NGUI element?

As i know “find” doesn’t work in this situation, like this:
healthSlider = GameObject.FindWithTag(“Enemy Health Bar”);

i’m so stupid:P

healthSlider = GameObject.FindWithTag("Enemy Health Bar").GetComponent<UISlider>();