use regex:

vb Code:
  1. Dim testStr As String = "Start: 29/09/2008 End: 29/09/2008"
  2. Dim rx As New Regex("(?<=Start: )\d{2}\/\d{2}\/\d{4}")
  3. Dim StartRange As String = rx.Match(testStr).Value
  4. rx = New Regex("(?<=End: )\d{2}\/\d{2}\/\d{4}")
  5. Dim EndRange As String = rx.Match(testStr).Value
  6. MsgBox(StartRange & vbCrLf & EndRange)

don't forget to import regex:

vb Code:
  1. Imports System.Text.RegularExpressions