internal class CustomComparer:IComparer
{
    private C1FlexGrid flex;
    bool _desc;

    public CustomComparer(C1FlexGrid flex, SortFlags order)
    {
        this.flex = flex;
        _desc = ((order & SortFlags.Descending) != 0);
    }

    public int Compare(object x, object y)
    {
        string s1 = (string)flex[((Row)x).Index, "Level"];
        string s2 = (string)flex[((Row)y).Index, "Level"];

        int icmp =(GetPostNumber(s1)> GetPostNumber(s2))?1:-1;
        // return sort order (ascending or descending)
        return (_desc) ? -icmp : icmp;
    }

    private int GetPostNumber(string s1)
    {
        var match = Regex.Match(s1, @"\d+$").Value;
        return Convert.ToInt32(match);
    }
}