This approach should work. You may also want to consider an "update matching records" version of Import Records. This method could eliminate the need for a script and additional table.
Note: It's often a good idea to make a back up copy of a file before performing this kind of import so that you can throw the file out and try again if you don't get the results you expected when you imported your records.
Thanks, that import technique worked nicely.
I would be interested in knowing how to build the script, is it complex?
A bit more complex than the import. However, there are cases where it makes sense to import into a secondary table--particularly when you can't be sure the data is perfect prior to import.
Here's the script skeleton:
Go To Layout [layoutname (Yourtemptable)]
Go To Record [First]
//put your set field steps here to process the data
Go To Record [Next ; Exit after last]