There was a census done in Balmaclellan in 1792. There were Griersons in Knocklearn, Crogo, Barmark and Parkrobin at the time I think the one you may want would be the Barmark where William Grierson aged 70 Isabel Kevan 63,Isabel Grierson 38, William Grierson 30,James Grierson 28, Agnes Paulin 60, Elizabeth McCaa 22, Agnes Gillespie 20. These were the inhabitants at the time. Perhaps your ancestors were amongst these?
MI's for Balmaclellan include Gillespie and Grierson names.