Hi bimseun

Assuming Name and Mark are in A1 and B1, you could prefix your formula
with:

=IF(AND(A1="",B1=""),"", ...the rest of your formula

or you could leave the formula as is and use conditional formatting to
make the font the same colour as the cell (white?), use
=AND(A1="",B1="")

To hide the formula in the Formula Bar, format the cells and check
Hidden on the Protection tab - the formula will "disappear" when you
apply the password protection (remember to uncheck Locked for the cells
you still want to edit).

Regards

Steve