The attached control is a custom TextBox that will automatically insert dashes between groups of characters. This is similar to the license key field displayed during the installation of Microsoft Office and other software. The user just types in the letters and/or numbers and the control will automatically insert dashes between each group for improved readability. The default length of groups is 5 characters but there is a property to change that. I would also recommend setting the MaxLength property appropriately, e.g. if you have 25 characters in a serial code then set the MaxLength to 29, to account for the extra 4 dash characters that will be added.