There’s about 78 papers in PRONI on the name Cromwell Price (I suspect there was more than 1 Cromwell Price), mostly in the series D552/B/1/1/xxx & D650/xxx & D1071/xxx
An example is D650/5 dated 28th Oct 1719, is one of the 3 lives leases I mentioned earlier:
Lease of three tenements and 17acres for three lives (Cromwell and Nicholas Price sons of lessor and John Meredith, Donaghadee) renewable for ever. Rent: £8 per annum + fees. (In dorso). Assignment by Rev. Charles Norris and Elizabeth Norris, Ballyloghan and Jane Williamson, Mount Alexander to Joseph Poulter, Saintfield, Consideration: £10. Hon. Col. Nichs. Price, Hollymount, Co. Down to Jane Meredith, Legigoan, Co. Down. Relating to Saintfield Town and Ballyagherty, Co. Down.
He seems to have been one of the MPs for the Downpatrick area and so there’s a fair amount of correspondence between him and other dignitaries. You would need to work your way through them to see if there is any mention of Manary.
http://apps.proni.gov.uk/DCAL_PRONI_eCatNI_IE/SearchPage.aspx
Bear in mind the catalogue only has a summary of each document. If you want to see the full document, you either need to go in person or pay PRONI to copy them for you.