Run a macro in active cell only. Want to place current date/time.

[time clock watcher]

Would like to make a Gate sign in sheet with a macro named ("GateIN") that
will return the current date/time in the active cell only. When the same
macro is run in an other cell I'd like the later current time to be entered
but leave the previous cell un-touched.

 

[Luke M]

Sub GateIN()
ActiveCell.value = Now
End sub