I created a ocx that has a method,

[id(5), helpstring("????Test1")] void Test1(VARIANT* a);

the implementation is
void Cocx030820Ctrl::Test1(VARIANT* a)
{
try
{
 //see here
AFX_MANAGE_STATE(AfxGetStaticModuleState());

ST_PRINT* m;
 //get data
m=(ST_PRINT*)a;
CString s;
s.Format("%d,%d,%s,%c",m->i,m->l,m->s,m->mSTRU1.c);
 MessageBox(s);
}
catch(...)
{
 MessageBox("f");
}
}

and the ST_PRINT definition is

#ifndef IOPRINT
   #define IOPRINT
   typedef struct
   {
unsigned char a[11];
unsigned char b[9];
char c;
   }STRU1;

   typedef struct
   {
unsigned char Tran[11];
unsigned char TermId[9];
STRU1 mSTRU1;
char c;
int i;
long l;
double d;
char s[10];
   }ST_PRINT;

#endif

My question is how to call the Test1 method in C#
   //ST_PRINT
   object obj=new object();
                                  how can I set the field value of obj.
   axocx0308201.Test1(ref b3);

Thank you very much!