Efficient V'*S*V matrix multiplication?

I have a matrix V with orthonormal columns, order n x k, and a symmetric, indefinite, matrix Z. Is there a lapack or blas routing to efficiently do the multiplication

V'*Z*V

If I do this in matlab, the result is NOT a symmetric matrix and has to be symmetrized and the result has roundoff of order 1e-13 for n approx 1,000

[James Tursa]

Do you have a C/C++ compiler installed where a mex routine could get at the BLAS symmetric matrix multiply routines directly? Are your matrices real or complex?