Update real work allocation manually

I need to make a lot of changes in the real work allocation for a bunch of resources. Doing it in the interface will take a long time.
So I've exported the concerned records from the table 'work' in a spreadsheet to define what has to be modified and I'm planning to prepare some update scripts to inject the changes directly into the table.
Looking at the code I realize that 'assignment' and 'planningelement' will have to be updated accordingly.
I know this is a dangerous operation, and backups will be there to cope with blocking errors, but it is a great opportunity to better understand how it works.

I was just wondering if records in assignment and planningelement are not recalculated each time that a change is done in the real work allocation. If it is the case, instead of preparing complicated updates for these 2 tables, I was wondering to implement changes in table work, then open real work allocation in the interface and update one record per concerned activity. Will this recalculate all fields in the mentioned tables?

Thanks for advices.
Ciao
Jean Pierre

Thanks for these comments, I'll let you know how it goes.