Check for installed Excel version, then load COM object library dynamically in C#

I am using Microsoft.Office.Interop.Excel to write data to an excel file in C#. I am using Excel 2010, so I have Microsoft Excel 14.0 Object Library added as reference.. But now I need to make the program work on Excel 2003 and above. So, I removed my reference to Microsoft Excel 14.0 Object Library and now looking for a way to check the installed Excel version on the machine then use it's COM object library.

Currently, I use this code for checking the version, but it returns "2007" instead of "2010". What am I doing wrong?

 namespace OfficeVersionCheck
{
    using System;
    using Microsoft.Win32;

    class Program
    {
        static void Main(string[] args)
        {
            RegistryKey localMachine = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\Office\");

            string version = string.Empty;

            foreach (string key in localMachine.GetSubKeyNames())
            {
                if (key == "11.0")
                    version = "2003";
                else if (key == "12.0")
                    version = "2007";
                else if (key == "14.0")
                    version = "2010";

                if (!string.IsNullOrEmpty(version))
                {
                    break;
                }
            }

            Console.Write(version);

            Console.ReadKey();
        }
    }
}

Now after checking the version, I need to load its COM object library to use in my program. Is there a way to do this? Any help would be appreciated. Thanks in advance.