MISO transfer function estimation using tfest/oe with apriori structure constraints

I woule like to estimate a MISO transfer function using the commands, for instance, tfest,with apriori structure constraints.

For example I would like to force the following structure (the denominator polynomials of the two inputs u1(t) and u2(t) to have the same structure and values (na input, number of poles).

y(t) = B1(z)/A(z) * u1(t) + B2(z)/A(z) * u2(t)

Is it possible?

[ArchLucs]

If you need more information please let me know. I would really like a feedback from anyone. Thanks