Basic MS Access question

I am trying to calculate the difference between 2 dates in an MS Access Query, and then have that difference impact the addition of a value to a new column.

I have [PepsiDate] and [VisitDate] from a couple of
For example, the first date is [PepsiDate] and the second date is [VisitDate].  If [VisitDate] - [PepsiDate] is within 7 days, I want to update a new column [PepsiWithin7] to say 'Yes.'

Is there a way to create this populating? or for the new field to maybe just subtract dates the way I've described?

x-posted to ms_access