Creating New Cell Styles
You can create new cell styles by defining them in the style sheet. To define a new cell style:
1. Select a style definition cell within the style sheet. It is best to choose a cell style that is similar to the desired style.
2. Copy and paste the cell in the style sheet. You now have two copies of the style definition cell.
3. Unformat one copy of the cell using Format Show Expression.
4. In the command StyleData["name"], change name so it is representative of the style. It should not be the same name as any other cell style in the sheet.
5. You can then either reformat the cell and set the options, or type in the options directly while the cell is unformatted.
A new cell style is now present in the style sheet and can be used in any notebook that refers to this style sheet.