Locking Data
 

I have a spreadsheet where a co-worker and I keep track of online courses we
build into our online platform. We create tabs within the spreadsheet to
separate out the 1st and 2nd halves of the semester courses (by course start
date). When we are finished building a course, we move all that data (all in
one row) from the semester tab to a tab called "Completed". However, I've
set up some formulas to calculate the number of anticipated courses (in the
semester tab) vs. the number of actual courses we worked on (in the
"Completed" tab). Is there some way to "lock" the data I am analyzing for
the anticipated semester so that once we are done figuring this out we cannot
add more to it? Can I set a date range on cells so that I can't enter data
before or after specific dates?