A compound error is any combination of burst errors with various burst lengths including random errors. The compound weight of any such error is defined as a kind of combinational metric which is a generalization of Gabidulin's metric. First, we present a fast method for calculating the weight of any word. Based on this method, as an extension of Wadayama's augmenting method in the case of Hamming weight, we propose a method of constructing codes having higher coding rate by augmenting any compound-error-correcting codes. Furthermore, we show some examples of good compound-error-correcting codes obtained by using our augmenting method.