Dim pattern As String = "\[\w+(?=\])\]"
Dim txt = "13[246]57[98]1223"
Dim rgx = new System.Text.RegularExpressions.Regex(pattern, System.Text.RegularExpressions.RegexOptions.IgnoreCase)
For Each match As System.Text.RegularExpressions.Match In rgx.Matches(txt)
Output.Show(match.Value )
Next