I have a question, why are you using the same cell for data entry as the
cell for your formula or do I not understand your question?
A good practice is to use cell (A) for your formulas then hide row (A) to
protect your sheet formulas..
use row (B) for data entry and color code row (B) font using conditional
formatting and place your answer in row (D) and use conditional formatting
for Answers..
Hopefully this will help you protect your formulas..

"Edward" wrote:

My question is stupid but simple:

I have two spreadsheets, spreadsheet A & B, I tried to copy the most
simplest formula from A to B, and i expect the formula is retained in
B, e.g., in cell A1of A : =(1)+(2), then copy to B, it's still
=(1)+(2), very simple right?

The problem is it suddenly not working in one of my office computers,
yes, only one, then weird thing is, when I try the copy function
above, the cell in B only have the value inside, i.e., 3, but not the
formula =(1)+(2), (seems like paste by values, but what I did is only
Ctrl+c and Ctrl+v), when i try to use paste by values, I was promoted
that I need to insert a object something. very strange.

Just would like to know if this related to settings something?

Thanks in advance.