another blanchard quah decomp

[obicna89]

hi!

i am using a bivariate VAR, and that means i have to impose one restriction on the long run matrix C.
but theory i am testing says i need to impose the restriction that if we are looking at the coefficents of C:
c11 c12
c21 c22
i have to impose that c12 = -c22. can i do that and how?
c11 and c21 are NA, but how can i impose aforementioned restriction?