Validate DevExpress Quantum Grid Field before Post

I am using Delphi and DevExpress Quantum Grid 6.  Sometimes users don't fill in the necessary entries before posting which generates SQL "cannot insert NULL" errors in the application.  I have tried to fix this on the Dataset level but canceling the post makes the user lose the data they have entered without any warning (not a very good solution).  Is there any way to check the entries for empty (null) values before being passed to the dataset for posting?  I can't simply check in the field exit because often the users simply skip the fields or accidentally click on another row causing a pre-mature post.