I have the below C code I want to convert to VB. How do I convert the macro and union over?

c--------------
#define bf_N 16
#define S(x,i)(bf_S[i][x.w.byte##i])
union aword {
unsigned long word;
unsigned char byte [4];
struct {
unsigned int byte3:8;
unsigned int byte2:8;
unsigned int byte1:8;
unsigned int byte0:8;
} w;
};

vb-------------
Public Const bf_N As Integer = 16
Public Const S(x,i)(bf_S[i][x.w.byte##i])As ???????