VB里，编写求fac(n)=n!的函数，n值由文本框1输入，调用函数，求得结果输出到文本框2

Private Sub Command1_Click() Dim n As Integer n = Val(Text1.Text) Text2.Text = Str(fac(n)) End Sub Private Function fac(n As Integer) As Long Dim i As Integer Dim sum As Long sum = 1 For i = 1 To n sum