HI Claus, in addition to my above question i noticed one problem.

The purpose of this excercise is to ascertain gas cost based on usage shown in column C of the attached spreadsheet

The formula you had suggested worked with my previous example. But when i reduced the usage amount, the final result is not what i want.

PLease see attached

http://s000.tinyupload.com/?file_id=...01793090465492