The UpdateValue method calls ImplUpdateValue to respond when the user assigns a new value to this field. 

AActionRequest is interface of the action request object. ImplUpdateValue can use this interface to obtain information about the current request (such as the value the user assigned to this field). 

AFieldIndex is the index of this field in the set of field values that AActionRequest maintains. 

ImplUpdateValue generates an OnUpdateValue event so that you can apply the update using an event handler. If there is no OnUpdateValue event handler, ImplUpdateValue writes the current field value from AActionRequest to the associated dataset field. 

If ImplUpdateValue can't locate the dataset field to update, or if the request contained multiple values or a file reference rather than a value, ImplUpdateValue raises an exception.

UpdateValue 

Value 

OnUpdateValue 

Mode