The Expression Builder has three sections, located from top to bottom:
Expression box In the upper section of the builder is an expression box where you build the
expression. Use the lower section of the builder to create elements of the expression, and then paste these elements into the expression box to form an expression. You can also type parts of the expression directly into the expression box.
Operator
buttons In the middle section of the builder are buttons for commonly used
operators. If you click one of the operator buttons, the Expression Builder inserts the operator at the insertion point in the expression box. For a complete list of operators you can use in expressions, click the Operators folder in the lower-left box and the appropriate operator category in the middle box. The right box lists all operators in the selected category.
Expression
elements In the lower section of the builder are three boxes:
Note When you paste an identifier in your expression, the Expression Builder pastes only the parts of the identifier that are required in the current context. For example, if you start the Expression Builder from the property sheet of the Customers form, and then paste an identifier for the Visible property of the form in your expression, the Expression Builder pastes only the property name: Visible. If you use this expression outside the context of the form, you must include the full identifier: Forms![Customers].Visible