有谁能告书我function函数的用法！最好再附上简单的例子的源代码！

俺也是初学。从教材学的，共享吧。
函数是过程的另一种形式，它的执行结果返回一个值，所以，可以用在等号的右边，如：a=add(5)
语法格式为：
[Publice|Private|Friend][Static]Function name[(arglist)][as type]
[statements]
[name=expression]
[exit function]
[statements]
[name=expression]
end function

例:返回n个自然数的和
Option Explicit

Function addn(n As Integer) As Long
Dim i As Integer
Dim total As Long

total = 0
For i = 1 To n
total = total + i
Next i
addn = total '给函数赋值
End Function

Private Sub cmdadd_Click()
Dim A As Integer
Dim B As Long
A = txtnum.Text
B = addn(A) '调用函数并使用返回的函数值
txtshow.Text = B
End Sub

Private Sub cmdcls_Click()
txtnum.Text = ""
txtshow.Text = ""

End Sub

Private Sub cmdend_Click()
End
End Sub