David,
Just leave Parameter Types and Function Parameters emtpy
For example (in this case, call to a Windows API):
Call DLL "kernel32.dll" -- Function "GetUserDefaultLCID" () ()
The %_SB_RETURN% variable holds the return value.
BTW, there are interesting example scripts in the Examples package.
http://www.lindersoft.com/sb6_Examples.exe
We'll make new SetupBuilder 6.5 examples available next week.
Does this help?
Friedrich