as long as the totals in the total column remained formula driven (look
at the function cell "fx=" in your toolbar to see that it reads
=SUM(....:....) and not the same number as the cell you're in), you can
select the entire sheet (upper left square next to A and above 1) and
hit F9. This should re-calculate the entire worksheet.
You can also write a macro that clears all the cells into which you
enter numbers, and put it on a userform that pops up when you open the
workbook. You'd have one button to clear previous entries and another
to continue the current job. The way you'd do that is to select the
range of cells into which you enter data (for example G5:H60) and then
go to your toolbar, insert, name, define, and give it a name like
Estimate. Then the macro attached to the button to clear those cells
would read

Sub (whatever you name this button) ()
Sheets("sheet1").activate
This activates the sheet
Range("Estimate").clearcontents This
selects the range that you previously named and deletes all existing
data
Unload me
This unloads the user form and lets you into the workbook
End sub

And the macro attached to the button to continue with the previous
estimate would read simply:

Sub (yet another name for this button) ()
Unload me
End sub

If all your worksheets have cells that are linked one to the other, the
totals should refresh each time you hit save or re-open the workbook.
Or use that F9 key.

Joy