how to crect the error

[Angela2010]

Hi all .
I want to ask a question. I wrote a program , but when compiling , it reminds there are something wrong with the following code:

                  if(err = WFS_init (instr.selected_id, &instr.handle))
		handle_errors(err);

WFS_init () is one of the lib functions I used in the program and other lib functions are OK. What's more, the WFS_init() function also works well when I use it in other programs. the error is like this:

error C2664: 'WFS_init' : cannot convert parameter 2 from 'int *' to 'unsigned long *'
        Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or   function-style cast