Excel: String Tokenizer

I am trying to implement strings tokenizer in Excel via UDF using C# and Excel-Dna. Personally I found the mIRC's function $gettok pretty useful due to the lack of string functions in Excel.

Examples

getTok("Aquel que no espera vencer ya esta vencido",   1, 32) -> "Aquel"
getTok("Aquel que no espera vencer ya esta vencido",  -1, 32) -> "vencido"
getTok("Aquel que no espera vencer ya esta vencido", 2-4, 32) -> "que no espera"
getTok("Aquel que no espera vencer ya esta vencido",   0, 32) -> "Aquel que no espera vencer ya esta vencido"

Code

[ExcelFunction(Category="String Utilities", Name = "getTok")]
public static string getTok(string text, string token, int delimiter)
{
    int from = 0;
    int to = 0;

    string tokenPatter = @"(\d+)(-)(\d+)?";
    string[] tokens = text.Split(new char[] { (char)delimiter });

    Regex tokenRegex = new Regex(tokenPatter, RegexOptions.IgnoreCase);
    Match tokenMatch = tokenRegex.Match(token);

    if (tokenMatch.Success)
    {
        StringBuilder sb = new StringBuilder();
        from = short.Parse(tokenMatch.Groups[0].Value);

        if (tokenMatch.Groups.Count == 1) to = from;
        else if (tokenMatch.Groups.Count == 2) to = (short)tokens.Length;
        else to = short.Parse(tokenMatch.Groups[2].Value);

        for (int i = from; i <= to; i++)
        {
            sb.Append(tokens[i - 1] + ((char)delimiter));
        }

        return sb.ToString();
    }

    int index = int.Parse(token);
    if (index > 0) return tokens[index - 1];
    else return tokens[tokens.Length + index];    
}

Questions

• What would you improve from above code?
• Have you tried something similar with Excel?