This is a difficult one, Malcolm. There are a few McGreece that come up in the archives but they are a bit late for what you are looking. You can peruse them
here, although you probably already have this information.
What I did find was a
family tree that includes Hugh McGreece (1838) You may want to contact the owner of that page for further information
It is also possible that while the information you seek is not in the main database, it could be stored locally. The only place name you have mentioned there is in Tyrone. Assuming all these names come from the same area, there are 2 groups that may be able to shed some light on things for you.
The first is
County Tyrone Ireland Genealogy Research, They have records which can be accessed online via that link.
The second is
Tyrone's Historical society. Not so much for records, but more so, the local historical groups can often point you to actual events your ancestors were involved in or property they owned.
If there are other areas you are aware of, Just let me know and I can point you to the relevant groups in those areas too
Regards
Gordee