What do I need to do to correct this.
I have a column that will be filled in with numbers each week. Column B.
In column B I want a running total, subtracting one cell in B from the
previous cell.
I also want a grand total at the bottom to add up all the cells in column C.

EX. B C
3 157
4 155 2
5 152 3 and so on.

If I put the formula =B3-B4 and so on down the column I get the correct
answer in C4 but in column C5,C6 etc it shows 155 until I put something in
the B5. Column then shows the higher number which is the 155. Is there a
way to enter the formula OR the correct formula to do what I want or is this
unrealistic?