Open or ask file, or other?

[Simon Lord]

I'd like to get the user to select any file they wish via the 
file browser on their default OS.  In this case I'm talking 
about the Mac OSX OS.  I'd like a dialog box to open which 
allows them to click a file and select "ok" etc.  Problem is I 
can only seem to initiate the dialog box to do 1 thing, (1) they 
pick a name and location to save a file.  I briefly thought of 
the Open command but you need to know the path for that.

I seem to be suffering another brain fart, if someone can point 
me to the proper method to allow a user to pick a file  on their 
own via a file browser then it would go a long way to closing 
off this otherwise great weekend.

Sincerely,
Simon