Dear sir/madam:
Thank you for your letter of [date]。 I’m glad that you are also going to [place] next month。 It would be a great pleasure to meet you at the [exhibition/trade fair]。
Our pany is having a reception at [hotel] on the evening of [date] and I would be very pleased if you could attend。
I look forward to hearing from you soon。
Yours sincerely，
[name]