Thanks. However,  the command "series res= $uhat" works only whether I estimate my system  only equation by equation. To be clear, it works  whether I estimate  4 different equations by ols and then  collect  step by step the  residual of each regression by the above command and the RSS. It may work, but then I need the matrix residual sum of squares of the system of equations to pass at 2nd step to compute. Because at end I have to compute the test statistic