If you have referenced Excel why declare xlApp and xlWorkbook as Objects? Personally I would use late binding and not reference Excel. It may be a little slower but can be safer.
The problem though is using ActiveWorkbook.Save use xlWorkbook.Save as in my previous post and see if that works. This is both if you use early or late binding
UPDATE
I just checked and ActiveWorkBook did work if Excel is properly referenced but I would still use xlWorkbook
Sub RetrieveExcelValue()'Excel is referenced
Dim xlApp As Excel.Application
Dim xlWorkBook As Excel.Workbook
Dim ExcelValue As Double
Set xlApp = CreateObject("Excel.Application")
xlApp.Visible = True
Set xlWorkBook = xlApp.Workbooks.Open("C:/users/johns/desktop/test.xlsx")' my path of course
ExcelValue = xlWorkBook.Worksheets("PPT Transfer").Range("C5").Value
xlWorkBook.Save
xlApp.Quit
MsgBox ("The value of this range in Excel is " & ExcelValue)
End Sub