InfoPath Dev

I have a form with code behind. I am using a dropdown as filter criteria for a second dropdown in a repeating section. If I use the full xpath to dd1 it will always filter from the dropdown in row 1. I want to filter by the current row. Still unfamiliar with xpaths can some lend some help?

xpath filter =  /my:myFields/my:CommoditySummary/my:Line_Items/my:Commodity/my:Origination

xpath field =  /my:myFields/my:CommoditySummary/my:Line_Items/my:Commodity/my:Destination

I can never figure out if it is:

• my:Origination
• /my:Origination
• //my:Origination
• ../my:Origination

If you want to get a specific row of repeating data you'll need to specify the row number in your xpath.  Something like: /my:myFields/my:CommoditySummary/my:Line_Items/my:Commodity/my:Origination[current()].  The index should be on whatever node is repeating, so that may be the commodity group in your case.  This is for the xpath, but not 100% sure if this translates into code or whether there is a code specific way to do this.