HP-50g - Define functions with matrices inside

[slavhp]

Just buy a HP-50g, so i'm still a newbie here.

I need to define some functions with matrices inside, but it seem impossible.

An example:

DEFINE(A(M,R)=M*[[COS(R),1][1,COS(R)]])
or anything that contains a matrix inside, like:
DEFINE(A(B)=B*[[1,1][1,1]])

I'm writing the matrices with matrix writer.
Algebric mode
The "define" works well with every operation so far, but when I try to put any matrix inside, it shows "Bad argument type" error.

Thanks and sorry for the newbie question!