question about calldll

[Pete]

I am trying to use calldll to load a dll and call a function from that
dll in python.  I am having a problem when I use the get_proc_address. 
I have tried using several different strings as the procedure_name,  but
I always get a return value of 0,  meaning that there was an error in
trying to find the address (probably no procedure exits with that
name).  I tried using the name that is shown under the name column in
the output from dumpbin,  but I got the same error.  Can anyone tell me
what I'm doing wrong?

Also,  why is there both a in_args_format_string and an argument_tuple, 
what is the difference between these two?  And is the
result_format_string just anyold string?  It doesn't need to be defined
to be anything specific?