String tokenizer via UDF
In this statement:

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


The way that you have it written, I don't think that i will ever hit to.

Also, I would change some variable names to make it more readable. from and to got confusing, I had to keep telling myself that those are variables.  I recommend doing something like:

int intFrom;
int intTo;


at the very least, so that you automatically know that those are integer variables. 

Also you have an int for a delimiter? Why not just pass a char as a delimiter?

Other than that I think the code looks good.