The Ashfield Parish Church of Ireland in Kildrumsherdan Parish was established in 1821. It was called a chapel of ease, for the convenience of the people living out in the countryside.
This family that you are seeking may have belonged to either the Cootehill Church of Ireland, Drumgoon Parish with records starting in 1802, or the Killesherdoney Parish Church of Ireland in Kildrumsherdan which has records beginning in 1826.
The surname Wallace is often Presbyterian, and I find a Martha Wallace, born 1793, and baptised in the Seceder Presbyterian Meetinghouse. Her parents were Hugh Wallace and Mary Adams. Since weddings usually took place in the bride's church, you might want to check for a marriage in a Presbyterian Meetinghouse in the Cootehill area.
I may be able to do a lookup for you in the two Church of Ireland registers that I mentioned above. I would think that the Killesherdoney Ch of Ireland would be the best choice.