When I want to multiply a field I can say
But what if I want this over a selection of rows? I've selected Line 6-25 and for all I want to say
How do I say
Like most spreadsheets, Openoffice will handle this for you if you cut and paste the fomula, or select the region and use "Fill Down". If you have cell e.g. M9 containing =J9*K9, and you paste that into cell M10, it will automatically change that to =J10*K10.
Likewise for horizontal movement.
If you don't want it to do that, you have to put a $ in the relevant place: =$J9 * K$9 will always use column J for the first argument and row 9 for the second argument.