I want to populate the row id field with the random letters, when a new row is added.
--How to code the new row add event?
--How to refer to the id field in each row? When I used the client id, it always went to the first row.
I´d suggest giving the control a css class (e.g. myClass).
Then you can access the control using
As for the event, you can use
Since you're using the repeating section, you can add a calculated control and name it ctrl_calc_rep_sec_row_no. Always hide this control.
Add another calculated control using your random letters and named control of the above-calculated control to build your string.