Help with listcsv plug-in

[henk]

I need to prevent duplicate records to be imported via csv
Two of the fields in the row are 'old_ammount' and 'new_ammount',
old_ammount is the same as new_ammount of the previous row,
new_ammount is the same as old_ammount of the next row.
Before import I need to skip already imported rows untill
there is a match between previously new_ammount and importing old_ammount.
Then import can start with that row and rest of the rows.

I read that preventing duplicate records can be done by the listcsv plug-in,
but I couldn't find any clear explanation or example.

Does anyone has a hint?

 

[henk]

OK, found the solution myself (see attached file)
May not be idiot proof for every import file, but works perfect for me.