MATLAB: How to convert a vector to a row of a matrix and resize it at the same time in a special situation

Question

I want to convert a vector to a row of a matrix in a special situation which is necessary to resize it too as I explain.

for example:

vector A=[1 2 3]

should be the second row of matrix B in a special situation as shown below,as you see in the second row of the matrix B,after every two element zero we have a element of vector A.

B=[a b c d e f g h i;
0 0 1 0,0 2 0 0 3;
a1 b1 c1 d1 e1 f1 g1 h1 i1;
.. .. .. .. .. .. .. .. ..;]

My program is a large one and I need the way which is fast.

Answer 1

 B(2,:)=0;
 B(2,3:3:end)=A;