Typically you would call it from a query or elsewhere in code:
http://www.baldyweb.com/Function.htm
In other words, you'd call it from wherever you need its result.
Pbaldy, thank much for ur post. Can u explain the pop window come out when run function?
typically I can run subroutine method, why exact function can't do?
In explanation of the tutorial (attached text) said you can do (run).. why actually can't do in access?
How exactly are you trying to run it?