some worksheet columns don't update formula calculations
 

I have a worksheet where my sheet 1 is taking numbers from sheet 2 and 3 and
then using those numbers from sheet 2 and 3 to make calculations sum formulas
that I've inserted.
Some of the columns work fine, when I make a change to a cell 4, column 4 in
sheet 2, I notice the numbres change in sheet 1 and reflect the changes I
made to the cell in sheet 2, but some other columns don't work in sheet 2.
For example when I make a change to cell 4 in column 5, the numbers on sheet
1 don't reflect the change I made. The formula's on sheet 1 are correct and
are pointing to sheet 2. The only way the calculation works on sheet 1, is
that if I click on sheet 1 where the cell pointing to cell 4 in column 5 for
sheet 2 is and then hit enter. Any idea's why that is happening on certain
columns but not others?