Excel Spreadsheet anomaly

[Sweet G]

Hello, I am puzzled by what my spreadsheet does:

In cell A1 I enter '4'
In cell B1 I enter '2'
In cell C1 I enter a formula to multiply A1 and B1
it produces the answer '8'.

Fine so far but If I change cell A1 to '5' or B1 to '3' the answer in C1 remains at '8' until I click into C1 and then it performs the correct calculation.

Usually IME C1 automatically comes up with a new answer when either or both of cells A1 or B1 are changed. (Am using an existing spreadsheet in new job)

Why does C1 only perform the calculation when the cell is clicked into?
How do I ensure cell C1 automatically calculates when I make changes to cells A1 and B1?

Hope that makes sense

Thanks in advance

[Davethedog]

Go into TOOLS - Then OPTIONS.

Click on the CALCULATION tab and make sure that the automatic radio button is on as opposed to manual.

[ACtheTROLL]

or press f9

[Sweet G]

Many, many thanks. it was doing my head in!!!!!