No sign of any marriage record for your couple, but that is not unusual given the timescale.
There is no townland listed in County Armagh as Drumin (nor Levarghey area), albeit some start with these letters. If you go to
http://www.thecore.com/seanruad/ and type Drumin in the townland box and then choose 'at beginning of field' from the adjacent drop down menu, then choose Armagh from the County drop down menu, it will give you a list (you could just type 'drum' if you want to see a longer list of possibilities.
The Freeholders list of County Down does have a Graham Armstrong recorded at Ballymcanallane, which may actually have been Ballymacanallen. Although in Down, this was in the border area with County Armagh, and I have seen families in my own research living on either side of the border at varying times, so it may be worth you researching further. It would not have been unusual for the marriage to take place in the bride's townland area, and the Joyce surname was certainly in the border area of Armagh in timescale.
