Selena Gomez will be chatting live on UStream tonight about her experiences as the youngest UNICEF ambassador, including her recent trip to Africa and the Trick-Or-Treat campaign she is heading for the second Halloween in a row.

Gomez, 17, is urging her fans to "make Halloween count" by Trick-Or-Treating for UNICEF this weekend to reach their $1 million goal, which will buy kids around the world the basics: clean water, food, health care and education.