Write an OnValidate event handler to validate any edits the user enters in a cell before focus leaves it. OnValidate gives applications an opportunity to provide more validation than the EditMask property of the corresponding TItemProp object can supply. 

OnValidate only occurs if the user edited the value of the cell that is about to lose focus. The OnValidate event handler can verify the value the user supplied, and if it is not acceptable, raise an exception. 

Keys 

Values 

ItemProps 

EditMask