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 company is having a reception at [hotel] on the evening of [date] and I would be very pleased if you could attend.
We look forward to receiving your reply at an early date.
Sincerely,
[name]
[title]
