Need Help with Datediff

[gonzod]

Need help quickly and I know this is a no brainer for everyone on this site.
What I have is an Access database with Case Opened, Case Closed and Days Open. What I did was use the Datediff to get the total days when Case Opened and Case Closed are populated and it worked but now I need it to populate the Days Open with the total days when Case Opened is filled and no date is in Case Closed. Basically I need it to count the days it is open using current date with the date it was opened. I know this is all jammed together but I am in a hurry. Thanks for any help!!

[weekend00]

datediff("d",caseOpenDate,now()) returns days since case open till now.

[gonzod]

This is what I have now

=DateDiff("d",[Case Open],[Case Closed])

can i combine them both to also count when case not closed?

[DaveT]

IIF(IsDate([CaseClosed]), DateDiff("d",[Case Open],[Case Closed]), DateDiff("d",[Case Open],Date())

[weekend00]

Or
=DateDiff("d",[Case Open],nz([Case Closed],now))

[gonzod]

Thanks Guys for all your help!!!