In Excell how do you get to calculate after clicking off of Calc

[flyingrace]

I copied and pasted a calculation from the Help display and when I clicked
off of the calculation. It should have calculated but didn't. I am using
Excel 2007.
=SUM(A2,-B2) was put in C2
=SUM(C2,A3,-B3) was put in C3
How do you get it to calculate? I clicked on a different cell in a
different row and column. I put numbers in A2,B2 and A3and B3 that the
example gave. The help had the title "Calculate a running balance". I
copied and pasted the example like helped told me to do. When that didn't
work I typed it in and it still didn't work.
flyingrace

 

[Max]

One possibility: calc mode's inadvertently at Manual mode (unknown to you, of
course). Press F9 key to recalc. OK? In xl03, one could simply click: Tools >
Options > Calculation tab, which contain the options to set/re-set calc
modes. Normally, set it to auto mode.

Another possibility: Cells were pre-formatted as TEXT (unknown to you, of
course) Try re-formatting as General/Number, then re-ENTER the formula (to
re-trigger it).