How to perform a vec or vech operation on a matrix.

Hello,

I am looking for a way to "half-vectorize" a matrix in Maxima.  I
couldn't find any "built-in" functions to do this, and my meager
attempts to write some loops to do this have failed.  I've tried

vecVar:zeromatrix(21,1);
k:1;
for j:1 thru 6 do
    (for i:j thru 6 do
        (vecVar[k,1]:Var[i,j],k:k+1));

where Var is a 6x6 matrix.  But this gives me an error

No such entry - `setelmx'
 -- an error.  To debug this try debugmode(true);

I get a similar error when I try to use the "setelmx" function directly.

Any help would be appreciated.

Thanks
McKay

(I am using Maxima through the Windows GUI wxMaxima 0.8.1.)