Maybe something based on:

Sub getNext()
Dim lngCount As Long
Dim lngOddslides As Long
Static rayOdd() As Long
Dim L As Long
Dim x As Integer
Dim nextSld As Long
lngCount = ActivePresentation.Slides.Count
lngOddslides = lngCount \ 2 + lngCount Mod 2
On Error Resume Next
Err.Clear
If UBound(rayOdd) < 1 Or rayOdd(1) = 0 Then
ReDim rayOdd(1 To lngOddslides)
For L = 1 To lngCount Step 2
x = x + 1
rayOdd(x) = L
Next L
End If
nextSld = Int(Rnd * (UBound(rayOdd))) + 1
SlideShowWindows(1).View.GotoSlide rayOdd(nextSld)
rayOdd(nextSld) = rayOdd(UBound(rayOdd))
If UBound(rayOdd) > 1 Then
ReDim Preserve rayOdd(1 To UBound(rayOdd) - 1)


Else: ReDim rayOdd(1 To 1)
End If
End Sub

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