You can use the Copy Master Details process to generate the initial button. You'll want to use Updates as the Master/Parent table and you'll want to select Copy From Current Record and Copy All Relationships (most likely). Once you've done that, you'll need a Summary field from Updates to Projects for the Max Record ID# from Updates. Then take that back down to Updates as a Lookup. Then, modify your formula to have an IF statement that compares the Record ID# of the Update to the Max Record ID# and if they're equal, use the Copy Master Detail formula.
