Also, at the moment if you "hook" a datablock, it supresses the strut of other labels which have been moved which can be very dangerous if left "hooked" in error (which they do say you shouldn't do)
It should be the responsibility of those writing/commisioning the software to ensure that what "you shouldn't do" can not be done.
When I was writing software (not safety critical) I was very aware that for every idiot proof system there was a system proof idiot! Test, test and test again - then get someone else to have a go.
dd
p.s. I am so glad I didn't become an ATCO after all.