Here is a bit of code I wrote a while back.  Copy it and put it into a
module.  Then you can call it when you want.

'----------------- Code starts ------------------------
Public Function fStripToNumbersOnly(ByVal varText As Variant) As String
'Takes input and returns only the numbers in the input.  Strips out
'all other characters.  Handles nulls, dates, numbers, and strings.

Const strNumbers As String = "0123456789"
Dim strOut As String
Dim intCount As Integer

  If Len(varText & "") = 0 Then
     strOut = ""

  Else
     varText = varText & ""
     For intCount = 1 To Len(varText)
        If InStr(1, strNumbers, Mid(varText, intCount, 1)) > 0 Then
           strOut = strOut & Mid(varText, intCount, 1)
        End If
     Next intCount
  End If

  fStripToNumbersOnly = strOut

End Function
'---------- Code ends ----------------