小小格式化的问题

我是一个刚入门的新手，自已照着书写了些代码，但出了点问题，希望那位高手路过指点一下是那里出了问题啊，谢谢了
Public Class 计算圆的面积
    Function CalculateAreaFromRadius(ByVal radius As Double) As Double
        Dim radiusSquared As Double
        radiusSquared = radius * radius
        Dim result As Double
        result = radiusSquared = radius * radius
        result = radiusSquared * Math.PI
        Return result
    End Function
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim area As Double
        area = CalculateAreaFromRadius(100)
        MessageBox.Show(area, "Area")
        Dim s As String
        s = String.Format("{0:area3}", area)
        MessageBox.Show("with formatting:" & s)
    End Sub

End Class
为什么
Dim s As String
        s = String.Format("{0:area3}", area)
        MessageBox.Show("with formatting:" & s)
这些代码无法格式化啊？？？？ --------------------编程问答-------------------- 帮你UP一下，贴子都沉了。 --------------------编程问答-------------------- s   =   String.Format("{0:area3}",   area) 中的 area3 是什么意思？

s   =   String.Format("{0}:area3",   area)
s   =   String.Format("{0:D3}",   area)

补充：.NET技术 ,  VB.NET