I searched the subscription site Roots Ireland and there are a number of Patrick McCabe baptismal records in Co. Cavan in the late 1700s but none in the parish of Denn. The Denn RC records start in the late 1850s.
There are also a number of McCabe records in the 1828 Tithe records for Denn civil parish. I assume you have already researched the Tithe records?
Let me know if you need additional info.