Well,

You beat me to the answer. But, if the date comes over as null, and you are displaying it as " / / ", it will still be null, not empty.

>>I could just add logic that would not try to update that field if my value is null for a date, thus leaving it null, but the logic is complex for the number of fields involved and so it would be simpler if there was a null value for a datetime field. How do I do a ctrl-0 in code?

I guess you are not using views.

BOb