Time problem in Excel

Im trying to create a “clocking in” program for staff in Excel. I’ve had no problem creating the basic structure which allows the user to check box next to their name which then enters the system time. However, i’m not sure how to make the time “absolute”. It’s still dynamic after its been entered. I know that i can double cllick on the time then press F9 and this seems to do the trick – but i can’t expect users to have to do this every time they “clock in”. Have had no luck with macro either. Does anyone have any ideas?
Thanks