Wiat for Exec'd process to end

Simple question: How can I make NSIS wait for an application I started with 'Exec' to end?

I'm trying to copy a bunch of files using a special program, then compress them using another... so I can't have NSIS start all of the processes instantly, I need it to wait until the copying is done.

Sorry, forgot to mention that I realize you can make NSIS wait with a messagebox, but I'd rather automate the wait

Never mind, I'm an idiot and didn't see ExecWait