Using Date Fields in Word

In word 97/2000 I want to insert todays date at the top on my letter and then in another part of my letter insert a new date field that adds 15 days to that same date.( this would be similar to an invoice with a due date).
I currently use a word document that has a linked field to an excel sheet. When I open the word document it looks at the excel document(becuse of the link) and inserts the date from excel where I have the date calculation. It works Ok but, I would like to simplify the process (drop the excel Link )and just add 15 days to the date field(in Word) Thanks for any help or ideas