How to: Add, Modify, or Delete an Expression [Model Designer]
You can add expressions to folders and entities within Model Designer.
To add an expression
In the Tree view, select the model item.
On the Reporting Model menu, click New Expression.
In the Define Formula dialog box, build your expression, and then click OK.
In the Detail view, right-click the new expression and then click Rename.
Type a name for your expression.
In the Properties area, assign the properties that you want to apply to this field.
To modify an expression
In the Detail view, click the expression that you want to modify.
In the Properties area, click in the Expression box, and then click the Expression button.
Modify the expression and then click OK.
To delete an expression
In the Detail view, right-click the expression and then click Delete.