Hi Kiran262,
I have here a sample form with a trigger logic that sets the first row of the repeating table. If you check the rules on field 3, you will notice a condition that will only run if index = 1. The index field here uses a default value formula to determine the table's row numbers. This approach does not need coding, we simply used an index and a trigger action.
Another approach you can do is by hacking into the manifest file, locate the rule which sets field 2 to th value of field 1, and then modifiy the target field: field2 with the row number [1].
Hope this helps.
Regards,