Is it possible to post date a letter by 7 days by using fields? If not by using fields, is it possible to do this by using VBA code?

The background: When preparing financial accounts for self managed superannuation funds we prepare two packs for a clients. The first pack needs to be signed by our clients and sent back to our office before we send out the second pack. It is easier and more efficient to prepare both packs at the same time. Therefore I am looking for a way to post date the documents in the second pack by 7 days.