Reading/Filtering Distribution Group's Subgroups of an active directory?

Question

I've an Active Directory with domain myDomain.local, under it there exists a Distribution Group that contains many groups.
How can I read (programmatically) all these subgroups to retrieve a list of their names ?
And how to optimize the query to filter the result so that it just retrieves all the groups that ends with the word Region ?
BTW, I'm using C#.Net, ASP.Net and sharepoint, and i'm not experienced with AD.

Answer 1

Here's the solution I made; for those who are interested:

public ArrayList getGroups()
{
    // ACTIVE DIRECTORY AUTHENTICATION DATA
    string ADDomain = "myDomain.local";
    string ADBranchsOU = "Distribution Group";
    string ADUser = "Admin";
    string ADPassword = "password";

    // CREATE ACTIVE DIRECTORY ENTRY 
    DirectoryEntry ADRoot 
        = new DirectoryEntry("LDAP://OU=" + ADBranchsOU
                             + "," + getADDomainDCs(ADDomain),
                             ADUser, 
                             ADPassword);

    // CREATE ACTIVE DIRECTORY SEARCHER
    DirectorySearcher searcher = new DirectorySearcher(ADRoot);
    searcher.Filter = "(&(objectClass=group)(cn=* Region))";
    SearchResultCollection searchResults = searcher.FindAll();

    // ADDING ACTIVE DIRECTORY GROUPS TO LIST
    ArrayList list = new ArrayList();
    foreach (SearchResult result in searchResults)
    {
        string groupName = result.GetDirectoryEntry().Name.Trim().Substring(3);
        list.Add(groupName);
    }
    return list; 
}

public string getADDomainDCs(string ADDomain)
{
    return (!String.IsNullOrEmpty(ADDomain)) 
        ? "DC=" + ADDomain.Replace(".", ",DC=") 
        : ADDomain;
}