Complementing Databind information to a combo/list box.

Question

Hi. I am working in a connected environment using an application global dataset. In most dialogs, selectable options will relate to a table in the dataset. So I need just to populate the combo box with the total content of a column in a table. That's easy. The problem is that I sometimes would like to have an option or two that equals the DB value NULL or other predefined values which does not exist in the column with the other options. So instead of having only specific entries I would also have an entry in the selectable list which says "", "" and such. I do not want to add these to my global dataset. What is the easiest way of doing this but still maintaining a databind to a dataset (I know I can manually populating the list using a forward only reader and then adding the list, however I don't then have the advantage of the databind). Thankful for all replies.