How can I compute the expiry date of an equity option?

Equity option contract expires (stop trading) on 3rd Friday of the month.

To compute the expiry date:

1. Using NxNWkDay function, compute the calendar date of the third (3rd) Friday of the contract delivery month.
2. Using NxAdjust function, adjust the returned date in (1) using OBOE calendar and using "Following" for business day convention.