How do I Lock Cover in place?

Locking Cover

  Q.   When I run StaffCover I get a list of cover staff.  I then change some of the Covers to other staff using the Swap facility and do the Covers.  If subsequently I get a late staff absentee, I have to run the Cover again, the system reverts back to its original selection of staff cover which means that I have to reassign staff again.  Is there any way I can save the changes that I make so that if I get a late absentee it simply adds onto the list of Covers already created by me?

  A.   Before recalculating the Cover, Lock your existing Cover in place (via "Cover->Lock" or press F8).