Well, there are many ways you could change a line through code.
Since you have the data in an array, you could simple clear the textbox, and repopulate from the array. (See the previous post.)
If you need to do this in multiple places, you could create a class that inherits from the base array to hold your data. You add a property to the class that will take all the data in the array, and concatinates it to a string. Have the class use the databinding events to let the textbox know when a change occured, and bind the text box to the property. You could have the property let then have the logic step through the text and update the array (if the textbox is read/write).
I don't remember the data binding events off the top of my head, but they should be reasonable to find, and you are probably aware of them if you are doing data binding already.
John R Lick