Is it possible to make the value in a field dependant on another field without using VBA code.

ie

field1 field2 field3 (default of field3= KG)
81 aaa KG
81 bbb KG
81 ccc KG
82 ddd KG


What I am trying to do is still have the default value of field 3 set to KG but if in field1 a 81 is entered then make the default value of field3 EA ( Each) instead of KG
Can this be done without writing VBA code.

Any help or advise would be great, thanks ffor taking the time.

Locutus