How to compose fields in a List or DataGrid component?

I am going to use a List or DataGrid component very much like the one demonstrated in the tutorial “Using the DataGrid Component”, In my case, I am not constructing an array, I am using the XMLConnector and DataSet components much like the tutorial from Adobe, Data Integration: Using XML for a Timesheet "".

What I need to know is how do you use the fields moved between these data providers in order to create a new field composed of the other. In the Kirupa tutorial for example, I would like to use the component to create a new field out of the separate First and Last fields so that you have a new string, “Last, First” with the comma being an added part.
I think I see something in the documentation to suggest that it is possible through the component inspector using formatting, but I see no useful documentation actually explaining how to do it.

Any and all tips or clues would be appreciated, even a reference would help.