I would like to set up a spread sheet. My objective is to assign a cell(eg
A1) a value, say 50, but also to have that value hiden.

Then if i was to type in 40 into cell A1 it would work out the difference
for me i.e. the cell(A1) would show -10. Or alternatively if typed a value
say 60 into cell A1 the cell would display +10.

Is this possible? If so how? Many thanks