Qt widen QScrollBar when hover using StyleSheet

[Wahsekim]

I'm trying to change the width of a vertical QScrollBar with a custom stylesheet like
@QScrollBar:vertical
{
border: 2px solid grey;
background: #32CC99;
width: 10px;
margin: 22px 0 22px 0;
}
QScrollBar:vertical:hover {
background: red;
width: 25px ;
}@

It doesn't work. Did I make any mistake? Can't we change the width of widget in run-time?

[Wahsekim]

I have the solution. I sub classed QScrollBar and set the style sheet in enterEvent and leaveEvent. It works fine for me.