Creating a macro that replaces an image in multiple PowerPoints

Hi there, Please can you help me with the following VBA. I am trying to replace the first image that is on slide 1 of multiple Powerpoints within a folder. I want to replace the image with a new image that is saved on my desktop. I am also deleting another image on the page. The names vary from powerpoint to powerpoint in a series of 500 which is why I am looping this through a folder of powerpoints. I am not worried about the positioning of the logo yet I can do that bit I just can't get this code to open a series without crashing. Any help would be appreciated.

Private Sub CommandButton1_Click()
Dim oPPApp As Object, oPPPrsn As Object
Dim oPPSlide As Object, oPPShape1 As Object, oPPShape2 As Object
Dim FlName As String
Dim gfilename As String
Dim strfilename As String
Dim strfoldername As String
Dim pp As Presentation
strfoldername = "C:\PowerPoint folder"
strfilename = Dir(strfoldername & "\*.ppt*")
Do While Len(strfilename) > 0
'~~> Change this to the relevant file
FlName = strfilename
gfilename = "C:\Users\me\Desktop\logo.jpg"
'~~> Establish an PowerPoint application object
On Error Resume Next
Set oPPApp = GetObject(, "PowerPoint.Application")
If Err.Number <> 0 Then
Set oPPApp = CreateObject("PowerPoint.Application")
End If
Err.Clear
On Error GoTo 0
oPPApp.Visible = True
'~~> Open the relevant powerpoint file
Set oPPPrsn = oPPApp.Presentations.Open(FlName)
'~~> Change this to the relevant slide which has the shape
Set oPPSlide = oPPPrsn.Slides(1)
'~~> This is the shape which will be replaced
Set oPPShape1 = oPPSlide.Shapes(1)
oPPShape1.Delete
Set oPPShape2 = oPPSlide.Shapes(2)
oPPShape2.Delete
pp.Save
pp.Close
Loop
End Sub

There is one line of code which seems to be failing and not opening up the Powerpoint. Are you able to see the error?

Cheers, Catherine