Need to change VBA code from creating new PowerPoint to open an existing PowerPoint

I have an Excel document that I need to paste into PowerPoint. I found this VBA code online and it works great. My only issue is it creates a new PowerPoint presentation every time it runs. Instead, I would like the code to insert the slide into an existing file I created. Any help would be greatly appreciated. Thanks!

Sub WorkbooktoPowerPoint()

    Dim pp As Object
    Dim PPPres As Object
    Dim PPSlide As Object
    Dim Rng As Range

    Set pp = CreateObject("PowerPoint.Application")
    Set PPPres = pp.Presentations.Add
    pp.Visible = True
    Set Rng = ActiveSheet.Range("AA104:AU138")

    Rng.Copy

    SlideCount = PPPres.Slides.Count
    Set PPSlide = PPPres.Slides.Add(SlideCount + 1, 12)

    PPSlide.Shapes.PasteSpecial ppPasteOLEObject
    PPSlide.Shapes(1).Select
    pp.ActiveWindow.Selection.ShapeRange.Align msoAlignTops, True
    pp.ActiveWindow.Selection.ShapeRange.LockAspectRatio = msoTrue
    pp.ActiveWindow.Selection.ShapeRange.Top = 0
    pp.ActiveWindow.Selection.ShapeRange.Left = 0
    pp.ActiveWindow.Selection.ShapeRange.Width = 960

    pp.Activate
    Set PPSlide = Nothing
    Set PPPres = Nothing
    Set pp = Nothing

End Sub