I am creating a database of horses for my TAFE in ms access.

I have a horse table with horse, name and dam field. The dam is the female parent of the horse.

Appropriate data should be validated before it is accepted in the table:
  • A horse must not be deleted if its a dam of an existing horse.
    For example, Fionna cannot be deleted because she is Lara's dam.
  • A horse cannot be added that does not have an existing dam in the table
Code:
TblHorse:
   HorseNo  Integer (PK)
   Name     Text
   Dam      Text
   Color    Date
   Gender   Text
My table looks abit like this:
Horse Number / Name / Dam
585 / Lara / 458


658 / Pater / 288
584 / Mike / 323
458 / Fionna / 251
323/ Star/ 852
ETC....

How can I validate them in access?

Any help would be appreciated.