I am far from being an expert in Regex but with good tools writing a Regex become easier.
First, I suggest you to download is RegexBuilder from Renschler. This Regex tool is ideal once the Regex is created to check few sentence and to quick see if something is wrong or not.
The second tool is something for helping you to create the Regex. This Regex tool is also free by RadSoftware. You can download it here.
This tool is great to see what will be in your group and also contain a library of all Regex syntax.
With these two tools you should enjoy a little bit more the creation of Regex.