Checking for national dex script

[Guest Quothe]

Hello!

I am currently modifying on Pokemon Emerald for my own amusement and I want to make an NPC that checks if you have obtained the national dex or not. The basic idea is that I want him to block the safari zone entrance until you obtain the national dex and I wonder how I should go about doing that? I'd like him to say something like:

"Sorry, only people with the national dex can enter here" if i havent obtained it yet

"Oh, you have the national dex. You can enter." then he vanishes into thin air after screen blacking out. 

I am using advancemap if that is any help.