I forgot to mention that I have two arrays (records).
One for the modifiable elements, and one for the checkable elements.
If there is a conflict between the actual mod. item and one of the checkable items, the checkable item will move to the end of the modification list.
And the actual mod. item starting time could be changed in this process.
First I imagined a temporary table, but I felt this has too much overhead against an "in memory" array. UPDATE, INSERT, DELETE and reopen after each modification.