Here are some bits and bobs which gives a time-frame of Greenhill Farm:-
http://maps.nls.uk/os/25inch-england-and-wales/Click on "As individual sheets......... " under Browse Maps. Left hand box type in place name, i.e. Mucklow Hill, click on the drop down box, then click on a square, then on the right hand side it lists maps that are available for that section.
Dudley Archives Maps
http://gismo.dudley.gov.uk/public/historic/Default.aspClick on the box "I have read and accept the terms & conditions of use" Type in the box "Property name/number" Greenhill Cottages, submit, choose one of the 3 on list.
Extract from "Street Names of Stourbridge & Its Vicinity by H. Jack Haden published by The Black Country Society 1999"
.....Approached by a drive from the main road to Birmingham near Long Lane is Greenhill House, one of the oldest houses in the area to survive until the last decade of the 20th century, though much of its surroundings have been built on. In the early part of the 19th century Greenhill was the residence of the Darby family. The inscription on a stone in Halesowen Churchyard reads - ".....the earthly remains of Joseph Darby, late of Green Hill......
Newpaper article 11 Oct 1913 (FMP) - Sales: Farm Stock at Greenhill Farm, Halesowen
Newspaper article 2 July 1934 (FMP) - New Companies: Leasowes Building Co. Ltd. Darby family members of Greenhill Farm, Mucklows Hill, Halesowen etc. etc.
Will dated 1954 - William Henry Baker of The Croft Greenhill Farm Mucklow Hill Halesowen Worcestershire
Greenhill House apparently is a Grade 2 listed building. Your best bet would be to contact Dudley Archives & Local History Service.
Hope this helps.