DearSir/Madam，
Thankyouforyourletterof[date].I'mgladthatyouarealsogoingto[place]nextmonth.Itwouldbeagreatpleasuretomeetyouatthe[exhibition/tradefair].
Ourcompanyishavingareceptionat[hotel]ontheeveningof[date]andIwouldbeverypleasedifyoucouldattend.
Ilookforwardtohearingfromyousoon.
Yourssincerely，
[name]
[title]