Some DLL questions. Help would be appreciated

I have part of my indicator, which is a DLL.

My DLL requires analysis of past OHLC data, not just the current open, high, low, and close.

Is there a way that code in the DLL can reference the open, high, low, or close arrays or do they need to be passed in through the function call.

you need to pass the data in an array by reference, there are examples of this in the dll sample provided by metatrader