What denomination was Cecilia? If RC, Aghanloo is part of the RC parish of Limavady. Unfortunately their records dont start till 1855 so if thats where she was baptised or married, no RC records exist.
If Church of Ireland, their early records for Aghanloo were lost in the 1922 fire in Dublin, so again none to search.
If you can load the section of the birth certificate showing the 1843 marriage Ill see if I can tell you where it was.