Option Explicit

Sub DoSomething(strFile As String)

    Dim wb As Workbook
    Dim myPath As String
    Dim myFile As String
    Dim myExtension As String
    Dim FldrPicker As FileDialog

    'Optimize Macro Speed
    Application.ScreenUpdating = False
    Application.EnableEvents = False
    Application.Calculation = xlCalculationManual

    Set wb = Workbooks.Open(strFile)

    'Ensure Workbook has opened before moving on to next line of code
    DoEvents

    'Change First Worksheet's Background Fill Blue
    Application.Calculate
    ActiveWorkbook.RefreshAll
    Application.Wait (Now + TimeValue("0:00:10"))

    'Save and Close Workbook
    wb.Close SaveChanges:=True


    'Reset Macro Optimization Settings
    Application.EnableEvents = True
    Application.Calculation = xlCalculationAutomatic
    Application.ScreenUpdating = True

End Sub


Function GetFiles(ByVal Folder As String) As Collection

    Dim strFile As String

    Set GetFiles = New Collection
    strFile = Dir(Folder & "\*")

    Do While strFile <> ""
        GetFiles.Add strFile
        strFile = Dir
    Loop

End Function

Function GetFolders(ByVal Folder As String) As Collection

    Dim strFile As String
    Set GetFolders = New Collection

    strFile = Dir(Folder & "\*", vbDirectory)

    Do While strFile <> ""
        If GetAttr(Folder & "\" & strFile) And vbDirectory Then GetFolders.Add strFile
        strFile = Dir
    Loop

End Function

Sub LoopThroughSubfoldersAsWell()

    Dim colFoFi As Collection
    Dim varEl01 As Variant
    Dim varEl02 As Variant
    Dim varEl03 As Variant
    Dim strLine As String: strLine = "--------------------------"

    Dim strAddress As String: strAddress = "C:\Users\UserName\Desktop\Testing01\"

    Debug.Print strAddress
    Set colFoFi = GetFiles(strAddress)

    For Each varEl01 In colFoFi
        Debug.Print varEl01
    Next varEl01
    Debug.Print strLine

    Set colFoFi = GetFolders(strAddress)
    For Each varEl01 In colFoFi
        If Len(varEl01) > 2 Then  'to avoid some hidden stuff

            Set varEl02 = GetFiles(strAddress & varEl01)
            Debug.Print (strAddress & varEl01)

            For Each varEl03 In varEl02
                Debug.Print varEl03
                DoSomething (varEl03)
            Next varEl03

            Debug.Print strLine

        End If
    Next varEl01

End Sub