you said you wanted it in the header,
and you're right, it doesnt refresh up there the same as on the inside of a form.
if this was a form, you could use the top line in the form as an HTML row, and place the field there.
you can easily style it to make it jump out on the screen better.
but for a grid, if you wanted to get fancy, you could make it a VP with two content panels.
the top panel would show the System field, and the panel below the grid.