Well said and well done.
If I've read the post correctly, first time, when he said the girls in their prom dress were a turn on, you didn't tell him anything.
In this case, well done: it could have been just a playful comment, and he probably he did not even realize he said anything that could hurt.
You was very nice not to tell him anything.
Oogling over the girls three weeks later while he was with you was very rude and untactful. Well, I guess he didn't want to hurt you on purpose.
I think that perhaps from the other time, when he made that comment and you said nothing, he got the (wrong ) idea that you had no problems if he looked at attractive girls in your presence.
Perhaps he even thought "hey, what a nice lady! I joked and she ate not me alive ! perhaps she's so tolerant she'll let me watch ladies next time!let's give it a try, she might not be offended with it".
You voiced your concern, and did very well.
I don't think you overreacted at all, expecially because you were tolerant the first time.
Glad to know he apologized.
BTW, how long have you two been dating?
Is it a lot of time? And was it the very first time he acted like this?