Result of formula doesn't change when I change input (the value in a cell)

Hi,

I have a spreadsheet that I have been using for around 6 months. Suddenly, the formulas don't seem to be working.
When i manually enter a value in a cell the result of the formula, which uses the value in that cell as one of it's arguments, doesn't change.

Simple example:

say i had =A1 + B1

A1 = 10
B1 = 20
the result is 30

Now when I change A1 to 50 the formula still shows = A1 + B1 (as it should) but the result still shows 30, it doesn't change to 70.

I don't know why this happening. Any help would be very much appreciated.

Dave

Hi, Yes it was set to Manual. No idea how that happened!

Thanks very much

Dave