取出字符串中的中文、英文字母、数字自定义函数

用法：
=myget(字符串,1)   '取出中文字符
=myget(字符串,2)   '取出英文字母
=myget(字符串,0)      '取出数字
取出数字第2个参数可以省略，=myget(字符串)
参数start_num，可选择从字符串第几位开始取值，省略默认为1，至于要提取几位，可以外套个Left()。从第10位开始提取汉字： =myget(string,1,10)

Function MyGet(Srg As String, Optional n As Integer = False, Optional start_num As Integer = 1)

    Dim i As Integer
    Dim s, MyString As String
    Dim Bol As Boolean
   
    For i = start_num To Len(Srg)
        s = Mid(Srg, i, 1)
        If n = 1 Then
            Bol = Asc(s) < 0
        ElseIf n = 2 Then
            Bol = s Like "[a-z,A-Z]"
        ElseIf n = 0 Then
            Bol = s Like "#"
        End If
        If Bol Then MyString = MyString & s
    Next
   
    MyGet = IIf(n = 1 Or n = 2, MyString, Val(MyString))
   
End Function