I am not even sure how to phrase this question so I apologize in advance. I have a form used by our QA. it requires input of serial numbers - a lot of them (sometimes hundreds). I have two text boxes on the form for lower and upper numbers in the range (doesn't have to be this way but it is my best guess). I know how to to do this if it were just integers (see code below) but that is not the only format.Examples of the format could include a date code ("170508/1234") or could include alpha characters (ABC1234). there is a wide variety of formats but in every case, I want to find the range from the last set of numbers (typically last four digits - Like "170508/1234 170508/1235... and ABC1234 ABC1235 ... not to exclude 1234 1235 ....). 
Thank you in advance

```
 private void btnSN_Click(object sender, EventArgs e)
    {
        int from = Convert.ToInt32(txtSnStart.Text.Trim());
        int to = Convert.ToInt32(txtSnEnd.Text.Trim());

        for (int i = from; i <= to; i++) 

        {

           txtSN.Text +=  i.ToString() +" ";
        } 

```