This is the code that worked for me
concat("Delete /xpath=my:myFields/my:BPResults/my:BPSubmit[my:ID = '", ID, "']")
but it only works one column at a time. If I change more than one column my inserts stop working and the delete no longer works. I'm sure I need to get the current ID to get the exact row, but I'm not sure how to do it. I've tried putting a filter on the ID (which is the ID from the secondary source) but that doesn't work either. I'm at a loss. Would this be a better way to target the row I want deleted.
concat("Delete /xpath=my:myFields/my:BPResults/my:BPSubmit[last()]/my:ID =", ID) or would I replace last() with current()?