Hi Ray,
I was unable to find a Margaret Mackay baptised in Durness in 1798. There was a couple, Hugh Mackay and Barbara Mackay who were married Jan 9, 1788 as follows:
Hugh Mackay, alias macUstianmacUiliam macRory, in Hunleam, and BarbaraMackay, alias nin Nish from Melness
(Hugh Mackay, son of Hugh,son of William, son of Roderick/Rory) and (Barbara Mackay, daughter of Angus)
Baptism of their following children:
John 28 Jan, 1789
Angus 12 Nov, 1790
Eupham 6 Jan, 1793
Barbara 5 Apr, 1795
That's all I could see.
Ian