Need to Loop and return a value based upon data condition

A1 = Parent
B1 = Child
C1 = Status

Dataset:

ITEMA ITEMB OKAY
ITEMA ITEMC SHORT
ITEMA ITEMD OKAY
ITEMG ITEMF OKAY
ITEMG ITEMA OKAY
ITEMR ITEMP SHORT
ITEMR ITEMQ SHORT

I need to populate column D with the following logic - Loop Column A - find the 3 rows labeled ITEMA (they will always be grouped together) - if all column C = 'OKAY' then populate a new column with 'Good' or if any of the three rows have a 'SHORT' then return 'Not Good'.......then go to the next group and repeat, etc......

In the following dataset the result would be:

ITEMA ITEMB OKAY Not Good
ITEMA ITEMC SHORT Not Good
ITEMA ITEMD OKAY Not Good
ITEMG ITEMF OKAY Good
ITEMG ITEMA OKAY Good
ITEMR ITEMP SHORT Not Good
ITEMR ITEMQ SHORT Not Good

Any suggestions would be appreciated...........