Your best source of information for this is going to be the WP All Import documentation. I would look into creating a custom function that is run for a specific field http://www.wpallimport.com/documentation/advanced/execute-php/… but other than that, I don’t know how you would get what you want. You should contact the support for WPAI, they are usually extremely helpful with this type of thing and they may already have some example code available. Any time I ask them something they generally send me a link to a gist that solves the problem.
