Dim altNumber() As Integer = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9"}
Dim dd() As Char
Dim i As Integer
dd = TextBox1.Text.ToCharArray
Dim str As String
For i = 0 To dd.Length - 1
If IsNumeric(dd(i)) Then
str = str & dd(i).ToString.Replace(dd(i), altNumber(CInt(dd(i).ToString)))
Else
str = str & dd(i)
End If
Next