+=item balance_date_range START_TIME [ END_TIME [ OPTION => VALUE ... ] ]
+
+Returns the balance for this customer, only considering invoices with date
+earlier than START_TIME, and optionally not later than END_TIME
+(total_owed_date minus total_unapplied_credits minus total_unapplied_payments).
+
+Times are specified as SQL fragments or numeric
+UNIX timestamps; see L<perlfunc/"time">). Also see L<Time::Local> and
+L<Date::Parse> for conversion functions. The empty string can be passed
+to disable that time constraint completely.
+
+Available options are:
+
+=over 4
+
+=item unapplied_date
+
+set to true to disregard unapplied credits, payments and refunds outside the specified time period - by default the time period restriction only applies to invoices (useful for reporting, probably a bad idea for event triggering)
+
+=back
+
+=cut
+
+sub balance_date_range {
+ my $self = shift;
+ my $sql = 'SELECT SUM('. $self->balance_date_sql(@_).
+ ') FROM cust_main WHERE custnum='. $self->custnum;
+ sprintf( "%.2f", $self->scalar_sql($sql) );
+}
+