The compiler is telling you that you need more that one argument passed in. This is not VB/VBA where there is a concept of optional parameters. C requires more attention to detail. The first argument to this function is a pointer to an element. You don't have one of these at this point in your code. Keep in mind that the element ref is NOT an element data type. Please review the MYAPP.CPP source code for a scan that will change element symbology.
HTH,