generate matrix from submatrices.

Hello

I'm probably asking something really basic, but I've not been able to have
it working: I'm trying to create a 9x9 matrix from 1x3 matrix:
something like:
                [  A    0   0 ]
                [  0    A   0 ]
                [  0    0   A ]
                [ B   0    0  ]
M=           [  0   B   0  ]
                [  0    0   B ]
                [ C   0    0  ]
                [  0   C   0  ]
                [  0    0   C ]

where A,B,C ar some 1x3 matrices.

Unfortunately, i can't have something better than

                [ [ a1  a2  1 ]   [ 0  0  0 ]    [ 0  0  0 ]  ]
                [                                                     ]
                [  [ 0  0  0 ]   [ a1  a2  1 ]   [ 0  0  0 ]  ]
                [                                                     ]
                [  [ 0  0  0 ]    [ 0  0  0 ]   [ a1  a2  1 ] ]
                [                                                     ]
                [ [ b1  b2  1 ]   [ 0  0  0 ]    [ 0  0  0 ]  ]
                [                                                     ]
                [  [ 0  0  0 ]   [ b1  b2  1 ]   [ 0  0  0 ]  ]
                [                                                     ]
                [  [ 0  0  0 ]    [ 0  0  0 ]   [ b1  b2  1 ] ]
                [                                                     ]
                [ [ c1  c2  1 ]   [ 0  0  0 ]    [ 0  0  0 ]  ]
                [                                                     ]
                [  [ 0  0  0 ]   [ c1  c2  1 ]   [ 0  0  0 ]  ]
                [                                                     ]
                [  [ 0  0  0 ]    [ 0  0  0 ]   [ c1  c2  1 ] ]

Ie i have a 9*3 matrix of 3x3 matrices instead of a 9x9 matrix.

Is there a way to change it ?

Thanks

Regards