GridView - Add Custom Column

[Loopsludge]

I have a GridView bound to a query. I need to add a column which is
not returned in the query. To do this, I've added a templatefield to
the GridView control and gave it a column header (text). But I can't
figure out how to write in the desired value
(e.Row.RowIndex.ToString()) to that column as each row is created.

In short can anyone show me how I can write a value
(e.Row.RowIndex.ToString()) into a GridView column on the RowCreated
event?

Thanks in advance,
Loopsludge