Executes a block of statements if no preceding statement block in a
  block IF construct was executed and if the value of a logical
  expression is true.  The block of statements starts immediately
  following the ELSE IF statement.  The block is terminated by
  another ELSE IF statement, an ELSE statement, or an END IF
  statement.  Statement format:

     ELSE IF (e) THEN

     Where e represents a logical expression.