Hello Averil. Thanks for reminding me. Yes, CR wrote in her Maughold book that the family was known as Kerruish Collum after an ancestor who died in 1633 and whose will is extant - but didn't you find out that it was his mother's will, not his?
There doesn't seem to be a Robert (Callom) bapt 19 Feb.1697/98 who would fit in anywhere on CR's Glen Vullen chart - were you able to find him?

Thanks.
Sue