A theme is a predefined set of formats including colors, fonts, and other effects that enhance an object"s appearance and usability. The office theme, which formats every other row in a datasheet with a gray background color to distinguish one row from another, is the default. It contains a box for entering the expression, an option for displaying and choosing common operators, and one or more lists of expression elements, such as table and field names. Creating a calculated field: formatting a calculated field, you can specify a particular format for a calculated field, just as you can for any field, by modifying its properties. When you click this button, a row labeled total appears at the bottom of the datasheet. Those records with the same value for the field are grouped together, and the datasheet displays one record for each group. Aggregate functions, which appear in the other columns of the design grid, provide statistical information for each group.