I've been tied up with CIIE for several weeks!

A: Hi Jessica. Would you like to join my birthday party this Sunday?
B:  oh Kathy. Thank you for inviting. I'd love to, but I have to work on that day.
A:Really? It's weekend!
B: Yes...you know...my company is going to display our new products in China International Import Expo. I have been tied up for several weeks. 
A: Sorry for that. But I believe you could do it well since this is not your first time to attend an expo on behalf of your company. 
B:Absolutely not, it wasn't the first time. We have attended this kind of expos for 3 times.
A: Wow~That's great! When did you attend it for the first time?
B: The first time was the World Expo in Shanghai in 2010.
A: Yeah~That was a big one. How was it?
B: Definitely~it was amazing and this kind of expo is a great opportunity for us. We are looking forward to showing our company to the world. 
A: Good luck with it.
B：Thanks. And BTW. Happy birthday to you. 

A: OK, I'll see you around.

B: Bye.