Ms Excel : Error Dragging Formula Down

all my excel workbooks seem to have some kind of formula lock on them? Simply needing to subtract column B from Colum A, so enter in my formula in row 1 and drag down to end of the file and I get the same figure displayed all the way down the column. If I then select one of the cells which should show the B minus A answer is reads correct, i.e B3-A3 however the displayed 'answer' is from B1-A1 all the way down?

Solutions : 
Click on the Formula's tab, and look the right hand side for the "Calulcation" ribbon and click on "Calculation Options".

It should be set to automatic.

Works fine with me