I can do it, but question the usefulness of this field. Do you plan to create dozens of such calcualtion fields all with different criteria? Wouldn't it make sense to perform a find or use a filtered portal to find and display records matching such criteria?
IF ( Active = "Active" and Air Day = "Monday" and Air Time = GetASTime ( "6:30 am" ) ; Client Name )
I intend to create a display of all Clients names in a grid:
across the top - day of the week
along the side - time of day
-such that all active clients will be displayed in their appropriate grid intersection. So yes, I was planning to create a unique formula for each intersection.
I've created such "every field is a calculation" layouts to produce cross tab like layouts in older, less capable version of Filemaker...
With FileMaker 11, I'd use filtered portals to put the records into rows and columns instead of using so many calculation fields. Take a look at this Calendar demo file and note how days of the week are arranged into rows and columns: http://www.4shared.com/file/6UAOV_RZ/Calendar.html
Of course, for your scheduling system, you'll need more sophisticated portal filtering formulas, but the demo may at least show you how that might work for you.