编程；VB 编写一个过程,用来计算下列表达式的值,并在事件过程中调用.S=1+1/2!+1/3!+...+1/n!

Private Sub Form_Activate()
a 5
End Sub
Sub a(n As Long)
Dim i As Long
For i = 1 To n
Sum = Sum + 1 / f(i)
Next i
Print Sum
End Sub
Function f(n As Long) As Long
Dim i As Long
f = 1
For i = 1 To n
f = f * i
Next i
End Function