Counter sums quantity of files in said folder but doesnt update unless double clicked

[BigError]

Option Compare Text
Option Explicit
 
Function CountFiles(Directory As String) As Double
     'Function purpose:  To count all files in a directory
    Dim fso As Object, _
    objFiles As Object
     
     'Create objects to get a count of files in the directory
    Set fso = CreateObject("Scripting.FileSystemObject")
    On Error Resume Next
    Set objFiles = fso.GetFolder(Directory).Files
    If Err.Number <> 0 Then
        CountFiles = 0
    Else
        CountFiles = objFiles.Count
    End If
    On Error GoTo 0
End Function

Sub TestCount()
     'To demonstrate the use of the CountFiles function
    Dim fso As Object
    Set fso = CreateObject("Scripting.FileSystemObject")
    If fso.folderexists(Selection) Then
        MsgBox "I found " & CountFiles(Selection) & " files in " & Selection, _
        vbOKOnly + vbInformation, CountFiles(Selection) & " files found!"
    Else
        MsgBox "Sorry, but I can't find the folder:  " & vbCrLf & Selection _
        & vbCrLf & "Please select a cell that has a valid" & vbCrLf & _
        "folder name in it!", vbOKOnly + vbCritical, "Error!"
    End If
     
End Sub

How do I get this to refresh or auto update?

Also I have no Idea what I'm doing as this script was pinched from another user of this fine website and community!