Replace 3rd Instance of string

The Regex.Replace method with MatchEvaluator parameter explained here http://msdn.microsoft.com/en-us/library/ms149475.aspx[^] can be used for this purpose as shown below:

Dim text As String = "This is sample COUGAR text containing COUGAR" & _
        " word COUGAR five times COUGAR which is to be COUGAR replaced "
Dim ind As Integer = 0
Dim modText As String = Regex.Replace(text,
    "\bCOUGAR\b", Function(m as Match)
        Ind += 1
        Return IF(ind = 3, "9294653", "PANTHER")
    End Function, RegexOptions.CultureInvariant)
Console.WriteLine(modText)
'output
'This is sample PANTHER text containing PANTHER
' word 9294653 five times PANTHER which is to be PANTHER replaced

The input text can be read from file using System.IO.File.ReadAllText and the output can be written to file using System.IO.File.WriteAllText as explained here http://msdn.microsoft.com/en-us/library/ms143368.aspx[^]

dk7
I am thinking that something is slightly off ... I implemented the code as:

Private Function ReplaceNth(CompleteString As String, occurence As Integer, Find As String, replace As String) As String
    Dim CheckOccurence As Integer = 1
    Dim NewString As String = CompleteString
    While NewString.IndexOf(Find) <> -1
        If occurence < CheckOccurence Then
            Dim temp As String = CompleteString.Substring(0, CompleteString.Length - NewString.Length)
            Return temp.Replace(Find, replace) & NewString
        Else
            Dim a As Integer = NewString.IndexOf(Find) + Find.Length
            NewString = NewString.Substring(a)
            CheckOccurence += 1
        End If
    End While
    Return "Not Found"
End Function

Dim newProjectFile as new StringBuilder
newProjectFile.append(ReplaceNth(my.computer.FileSystem.ReadAllText(myFile).Replace("COUGAR", "9294653879"), 3,"9294653879","PANTHER")

Then I used My.Computer.FileSyetem.WriteAllText to rewrite modified file

The result I got is:
the 1st,2nd & 3rd instances of COUGAR were changed to 9294653879 and the 4th instance was changed to PANTHER. The desired result is for instances 1st, 2nd and 4th to be changed to COUGAR and the 3rd to be PANTHER. Additionally, since COUGAR was 6 characters long, I need to delete 4 blank spaces after the 2nd instance where COUGAR became 9294653879.

Thanks for any help!