This would likely better be handled with a Macro.
However, it can be done with fields.
I would suggest that you prepare a template, rather than updating some document. Then use a CREATEDATE field as the basis. That will update each time you create a new document based on the template. You can get times from any of the date fields using a hh:mm picture switch.

You would be using an IF Field to test the time generated in the CREATEDATE and then give you either 7:00 p.m. or 11 p.m. as a result.
Again, a macro would probably be simpler.

Even simpler would likely be two templates. Pick the one you want to use.


I know you said you are using a template. The word "template" means something different in Word than it does in general English.