Adobe LiveCycle ES4 add new and update Access Database, Non-Null failure

I am using adobe livecycle es4 and I am trying to add a new record and then update it to an Access database. However, when i press update the error tells me that i cannot have Null values and it displays a check box field name. How can i allow a null value for a check box? Because when my form is used, not all of the check boxes will be checked