Check Balance selects nested expressions (for example,
parenthesized) outward from the insertion point. To select a
nested expression, select anywhere within the expression by
clicking. Choose Check Balance, and click to expand the
selection out to the next set of enclosed parentheses, brackets,
or braces. Each time you choose Check Balance, Mathematica
expands the selection in both directions until it finds pairs of
matching parentheses, brackets, or braces. Repeating the command
expands the selection one level at a time. You can use the Check
Balance command to check the structure of mathematical
expressions. For example, if you have unbalanced parentheses or
parentheses incorrectly balanced with brackets or braces,
Mathematica beeps. Choose Help ► Why the Beep? to identify the
mistake. If you position the insertion point inside a bracketed
expression and choose Check Balance, Mathematica should select
the whole expression. If not, you have a missing bracket
somewhere. Mathematica cannot balance a selection