[myalsailamy]

للاسف لم افهمك سابقا  ،،  على العموم عدلته  الان  ان شاء الله يكون المطلوب

كود :

       
        Dim SourceText As String = "WTY 78Z 49Q #@d XCF FG8 9WG"
        Dim oRegularExpressions As New System.Text.RegularExpressions.Regex("^[A-Za-z0-9]+$")
        Dim result As String = ""
        Dim strGroups() As String = SourceText.Split(" ")
        If strGroups.Length > 0 Then
            For Each Group As String In strGroups
                Dim matchlist As MatchCollection = oRegularExpressions.Matches(Group)
                If matchlist.Count > 0 Then
                    result += "8"
                Else
                    result += "*"
                End If
            Next
        End If
        TextBox2.Text = result