Close. You must buy before 4pm on the 16/8, because you must own at open on the 17/8 to receive the dividend. Otherwise your assumptions are correct.
But warning! At open on the 17th CBA SP will mostly likely drop by the exact dividend amount ($2) because many traders will be playing that exact game you refer to (assuming no other significant company news on that day). This happens across most div paying stocks and since traders use professional trading systems it is very hard for an individual to make it work. I see the appeal but for me its near impossible to do what you suggest, so I don't bother trying. If you want to attempt it I suggest broadening your time frame by a few weeks, so you hold long enough to get the div and have time for daily ups/downs to balance out the ex-div day drop.
CBA Price at posting:
$108.10 Sentiment: Hold Disclosure: Held
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