Didn't get an error as such, just can't get my head round how to do it.
As for the query by form I created a new form with unbound controls on, and used this code (from the microsoft site.) for the query
[forms]![myform]![field] Or [forms]![myform]![field] Is Null
It just gives the same results all the time no matter what parameters i change. (also couldn't figure out the checkboxes in this method either.)
the form then ran a macro which ran the query and displayed the results into a new form