I got two date field in ms acces.when I write a query I can calculate the difference between these t

I got two date field in ms acces.When I write a query I can calculate the difference between these two dates and what I want is when the second field is null then the difference should be with the current date.can u help me .

Look at the VBA DateSerial Function. It returns an exclusive number for each date. By subtracting the older serial number from the most recent, it will produce the number of days difference between the dates if that's what you're looking for.