Why wouldn't the formula cells get dynamically calculated when target cell
data is changed? Couldn't find anything about this in help files.

I have been using this worksheet for years and never saw this problem... a
simple 2-week payperiod timesheet ... Fourteen pair of cells in which I enter
start time and end time, and fourteen cells with a formula to compute hours
worked per day (difference between the daily pair). Also weekly and biweekly
totals.

The cells all calculated when I "saved" the file. Also when I
closed/reopened, it still won't evaluate the formula cell(s) when I change a
"data" cell. Only if I hit "save", or individually select each formula
cell, place the cursor in the function box, and press enter.

1) What happened?
2) What can I do to fix it.
3) Is there a command that I can run to "calculate all" functions in a sheet
(or workbook)?