Is it possible to lock access to a cell or cell range?

I know it is possible to lock a cell range and then protect the worksheet,
but the locked and protected range can still be referred to, even if I
disallow selecting of locked cells.

I.e. if I lock and protect Column A, disallowing selection of locked cells;
a user can insert a formula in an unlocked cell that referrs to the locked
cell, by typing, e.g. "=a1."

Maybe this is possible in Excel 2007 but not in my version (2003).
Thanks,
Mark