Dropdown Filter in Form with an ALL

[Dan_Oliphant]

I have created an APP that dispatches crews to different jobs.  I have two tables, crews (general info) and crew_dispatch (adding the crew to the job). The crew selected in the crew_dispatch form is a reference to the crews table.  I just added one column to the crew_dispatch table called [location].  The crews table has a column called [pref_location] - preferred location.  I am attempting to filter the dropdown on the form to only show the crew members that would be willing to work out of each location.  BUT I also want to be able to select "ALL" to show everyone.  The [location] is an EnumList, because people do work out of multiple locations.  the validif statement I came up with is 

CONTAINS([crew_name].[pref_location], [location])

but that doesn't take into account how to SHOW all by selecting "ALL" in the [location]

any help would be greatly appreciated

[Steve]

OR(
  IN([location], [crew_name].[pref_location]),
  IN("ALL", [crew_name].[pref_location])
)