First of all the need to use the UseDLL command to open the DLL (don't forget the UnUseDLL command at the end to close it)
Then specify the prototypes of the functions you wish to import. For example if you has a function called "test" in your "unzip.dll" which accepted a string and returned an integer you would define the prototype as.
prototype NUMBER UNZIP.test(STRING); (notice that you have to include the name of the DLL in the prototype.
Its important to make sure that the argument list for the function matches up. This is especially important when using a function from a C++ dll becaue of the way C++ mangles names. Therefore if using a C++ dll you must put the command "cdecl" after the word prototype.
It is then just a case of calling the function from within the script. For example to call the "test" function defined above you can use either of the following syntaxes
nResult = test(szTestString);
nResult = UNZIP.test(szTestString);
The second method is useful if you have multiple DLL files containing functions with the same name.
Hope this is of some help