I'm working on a movie database and have a table of titles and two other tables: DVD and VHS. If the TitleID appears in either of the other tables, I have that movie in that format.

On my data entry form, I have checkboxes for each format. After update, depending upon the checkbox value, either an append query runs adding the TitleID to the format table or a delete query to remove it. My problem is, setting the default value of the box. The query (With the title table left joining to the format tables) the form is based upon has fields like:

Iif([VHS].[TitleID] is null,0,-1)

I try setting the checkobox's default value to that field with no effect. How can I get the checkboxes intial/default value to be equal to the -1 or 0 value of the record?