Trond
In the mid-eighties I was on the design team for the Lisburne oil field on the North Slope of Alaska. We were told by our reservoir engineers to expect "significant" H2S concentrations in the produced gas. Since most of the surface equipment is housed, H2S detection was a topic...
Another option would be to name the cells you wish to refer to. Since Excel defines Names with $ signs, copy and paste works.
Defining Names also really helps with debugging later...
Profit = Revenue-Cost, is a lot easier to understand than F4=E3-B2