Import/export CSV files in GX developer

Hello All. I'm trying to minimise the pain involved in writing multiple identical (in structure) rungs in GX. I used the export function to create a csv (ok) and did a trial edit in Excel (ok) but when I used the import function I get the cryptic message "This file don't access. Conversion stopped". I started by importing to the open project that I took it from with the cursor on the LH margin, then a few other places, then created another project using the same cpu type, but always get the same message. Am I expecting too much? Thanks.

OK, I've cured the "Don't access" thing by closing the excel file before importing. However, no matter how I juggle the import settings that pop up next, the conversion always returns an error on every line up to line 100, at which point it gives up (me too). I have now tried exporting / importing without opening the file. Also tried as txt file. Always the same result.