Infopath repeating table - get field from current row
===

I have a repeating table in Infopath.  On a field change event, I need to execute a calculation to with data in the row in question.  How do I go about this in the code-behind (C#) and Xpath?

For example, I have a start date and end date.  In the code-behind the do a calculation to calculate the number of hours in the span.  This works for the first row, but not subsequent rows.  I know the way I wrote it so far only works for the first row, but how do I make this work for all rows?
 