请VB高手帮忙注释

Public Class Form1
Public Sub c(ByRef _b As Integer)
Dim a, b As Integer
b = 1
For a = 1 To 5
b *= a
Next
_b = b
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim j, _b As Integer
Call c(j)
Label1.Text = Label1.Text & ControlChars.CrLf & "5!的阶乘是：" & j.ToString
End Sub
End Class

还有就是为什么不能用(Byref sender As System.Object, ByVal e As System.EventArgs)

Public Sub c(ByRef _b As Integer)
Dim a, b As Integer
b = 1
For a = 1 To 5
b *= a
Next
_b = b
End Sub

这段就是所谓的求5的阶乘的子程序，但是b *= a这句似乎是C的语法(也许是我对VB研究还不透彻).

之所以不能用(Byref sender As System.Object,.....)是因为button控件规定的，它的事件函数的原型在微软编写button控件时就已经固定了，你不可随意更改的。