I guess reading from txt file doesnt have any problem and will be getting
updated data too. Also you can use auto events to load the macro at the load
of powerpoint.

Sub ReadTextToTextFrame()
'load data to textframe of a shape
ActivePresentation.Slides(1).Shapes(1).TextFrame.TextRange.Text =
GetText("C:\\test.txt")
End Sub
'http://www.exceluser.com/explore/questions/vba_textcols.htm
Function GetText(sFile As String) As String
  Dim nSourceFile As Integer, sText As String

  ''Close any open text files
  Close

  ''Get the number of the next free text file
  nSourceFile = FreeFile

  ''Write the entire file to sText
  Open sFile For Input As #nSourceFile
  sText = Input$(LOF(1), 1)
  Close

  GetText = sText
End Function

This function will load the data from txt file to the textframe. You can
call this fuction at the start up.
http://skp.mvps.org/autoevents.htm

Another option is to create an addin which populates data from the file