F9 is the keyboard short cut for "Calc Now" Go to Tools and Options then
the Calculation tab to see this option.

if you want to show a "random" number when you press the F9 - the function
you are looking for is Rand()

"help me please i´m lost" wrote:

i don´t know how to put in a formula the action that makes the shortcutkey
F9(gives another number in the cells with the function random)