hi,
xl has bo built in function for this and I am sure if you search the net
enought you might find one. but you can make one yourself.  oooo
Create a user form with a single text box.
in a standard module put this code.....
Private Sub showclock()
Load UserForm1
UserForm1.Show 0
Call Clock
End Sub
Private Sub Clock()
UserForm1.tb1.Value = Format(Now, "hh:mm:ss AM/PM")
Application.OnTime Now + TimeSerial(0, 0, 1), "clock"
End Sub

Attach the Private Sub showclock to a custom icon. done.

I got this code from this web site.....
http://www.mvps.org/dmcritchie/excel/datetime.htm
except their code puts the timer in a cell so i made a popup out of it.
Check this site out if yo want to know a thing or two about time and dates
in excel.

regards
FSt1