[Jeze-a-Belle]

I trained our Yorkie by leashing 100% of the time when outside. After a year, with walking around our "un-fenced" yard, she was trained to the point of not venturing passed our property line. There are times when the little kids are outside next door, she will "but" for them. We've often used a stern "SIT" voice with excellent results.
She'll stop and sit.
Being very curious, they need lots of leashed walks and time outside.
Good Luck....