Gradient at ghost cells only?

[billy at dem.uminho.pt]

Hi,

I need the gradient of 5 scalars at ghost cells and I was thinking of creating
5x3 vectors with VecCreateGhost(). Right now, I calculate the gradient during
each iteration and I don't store it's value. 
I would like to calculate, store and exchange the gradient at the ghost cells
only, to minimize memory requirements. How is the best way to do that?

Billy.