mixed prgraming - force passing argument

Hi
I am working on VS2010 mixed-programing and use the Intel Compiler / VisualStudio (Intel Parallel 2015) to compile my project in VS 2010.

Console - c source:

    #include <stdio.h>
    #include <stdlib.h>
    #include <conio.h>
    #include <string.h>

    //#define readfile readfile_

    extern void readfile(char*, int*);

    int main()
    {
        int n, count;
        char Fname[9];
        char Name[10];
        strcpy(Fname,"AMIN.for");
        fprintf( stderr, "%s\n", Fname);
        readfile( Fname, &n , strlen (Fname));
        fprintf( stderr, "n = %d\n", n);
    //  fprintf( stderr, "%s\n", Name);
        getch();
        return 0;
    }

Subroutine - Lib fortran:

          subroutine readfile( fname1, m )
          character fname1*(*)
          integer m
          integer iounit,i
          iounit=15
          write(*,*) fname1
    c10   format (a9)
          open(iounit,file = fname1,action='read')
          read (iounit,*) m
    c20    format (i10)
          write(*,*) m
          close(iounit)
          return
          end subroutine

    
I change setting to "lower Case" (Lib1:properties->fortran->External Procedure) and my project return "n=10" and I don't have a problem, BUT in this line I have a question

 readfile( Fname, &n, strlen(Fname) );

I want to change that line. I want compile without strlen like:

readfile( Fname, &n );

When i comiple my project,it can not open and return the contents of My file(AMIN.for).
I change setting for "Lib1" in property page->fortran->External Procedure :
" Calling conversion ----> (from "default" to "STDCALL") "
and I compile it again but it can not return the contents that I want(n=10).

I want to passed force from string lenght argumet with change setting or define a little function(any trick!).
how to do it?
excuse me for bad spelling