that's a bit trickier.
I assume you have some way of automatedly copying all the files to your backup_drive at a certain time?
=> Then try to implement an additional automatic reload of all the files prior to that copy_job with a conditional exit, like this for example:
IF TIME(FRAC(NOW()), 'HH:MM') = 17:00 THEN
[remember to leave one blank line to close of the loop]
I'm not quite sure about the syntax, you might need quotes or so, but this will effectively exit the script immediately and thus not load any data at that time - QlikView purges all the old data prior to loading new data by default, so the qvw files should then be empty <-> at all other times, that command will be ignored and the script should reload normally.