Here is a simple code function in C# .net asp .net to find string between two strings. 

            Response.Write(FindString("Hello World This is a Test","Hello","Test"));



 public String FindString(String str, String strStart, String strEnd)
        {
            if (str.Contains(strStart))
            {
                int iStart = str.IndexOf(strStart) + strStart.Length;
                int iEnd = str.IndexOf(strEnd, iStart);
                return str.Substring(iStart, (iEnd - iStart));
            }
            return "False";
        }


Use online converter to convert the code into VB .NET .