formulas showing up in empty cells all by themselves
 

I have a worksheet with many formulas for different cells based on the hour
of day. (S1-S8 for 0100-0800, T9-T12 for 0900-1200, U13-U1800 for 1300-1800,
T19-T23 for 1900-2300, S24 for 2400).
The problem is that the formulas are only input in the cells listed but in
the empty cells adjacent to cells with formulas the formula will input itself
when the data is input in the cell the formula above or beside it is looking
at/for. (T13 should be empty and is left blank when worksheet created but
when the data that U13 is looking at is input it seems like T13 is copying
the formula from T12 all by itself)
I have already remove the "allow data ranges to extend" selection in the
excel options area, I thought that worked but other users are still having
the problem. I checked their settings and they are the same as mine.

Any ideas? Please help!
Sorry, I tried to describe as best and clearly as I could!