How can I clear columns and rows of a matrix?

I have matrix like A which is in a square form p*p and a line matrix B in a form of q*1 (q<p).

I want to clear rows and columns of matrix A with the help of B. for example:

A=[1 2 3 4;5 6 7 8;9 10 11 12;1 2 3 4]

and

B=[2 4]

I should eliminate second row and column 'As B(1)=2' and fourth row and column 'As B(2)=4'.

So A becomes [1 3;9 11].

Answer 1

[Amit]

    A(B,:) = [];
    A(:,B) = [];

[Ayob]

I check it,but didn't work .

??? Subscripted assignment dimension mismatch.

[Amit]

I edited it and tested it. It works.