One half of the IIF expression is what to do if true, the other part is for what to do if it's not, so you don't use the logical operator "Not". you could use an event (AfterUpdate or LostFocus, or maybe even Change) on the textbox to set the checkbox to be True or False when that event fires. Or you could try =IIf(IsNull([AttachmentField]),0,-1).
IsEmpty is supposed to be used for a varaiant data type, which I doubt your textbox is.
Last edited by Micron; 01-25-2016 at 04:57 PM.
Reason: IsEmpty
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.