Here's some code I wrote recently for a church that uses PowerPoint for songs they sing. Naturally, as each song spans multiple slides, the same song title appears multiple times. Amongst other things, for my purposes the code automates Word rather than Excel and cleans up & formats both the output and titles themselves, as well as producing a sorted text file. For your purposes, you could use much the same code to automate Excel and do the sorting there without bothering with the text file. You may or may not want some of the other tweaks I mentioned.
Sub GetTitles()
Dim WdApp As New Word.Application, wdDoc As Word.Document, DataArray() As String
Dim Sld As Slide, StrTmp As String, StrNms As String, StrFlNm As String
StrFlNm = ActivePresentation.Path & "\Titles.txt"
Set wdDoc = WdApp.Documents.Add
For Each Sld In ActivePresentation.Slides
With Sld
If .Shapes.Count > 0 Then
With .Shapes(1)
If .Type = msoPlaceholder Then
StrTmp = Trim(Replace(Split(Split(.TextFrame.TextRange.Text, vbCr)(0), Chr(11))(0), " ", " "))
If InStr(StrNms, StrTmp) = 0 Then
wdDoc.Range.Text = StrTmp
wdDoc.Range.Case = wdTitleWord
StrTmp = wdDoc.Range.Text
StrNms = StrNms & StrTmp
End If
If .TextFrame.TextRange.Text <> StrTmp Then .TextFrame.TextRange.Text = StrTmp
End If
End With
End If
End With
Next
StrNms = Left(StrNms, Len(StrNms) - 1)
DataArray() = Split(StrNms, vbCr)
WdApp.WordBasic.SortArray DataArray()
wdDoc.Range.Text = Join(DataArray(), vbCr)
wdDoc.SaveAs2 FileName:=StrFlNm, FileFormat:=wdFormatText, AddToRecentFiles:=False
wdDoc.Close False: WdApp.Quit
Set wdDoc = Nothing: Set WdApp = Nothing
End Sub