1)   Select tools | customize
2)   Select the tools tab
3)   In the menu contents window, scroll down to an open line
4)   Type NASM (or what ever you want to call the option)
5)   Below in the command text box add NASMW.EXE
6)   In the arguments line add
 -f win32 -l $(FileName).lst $(FileName)$(FileExt)

Now you may select tools | NASM with an .ASM file active in Visual C++
and make an .OBJ file (or force C++ to rebuild the .OBJ file with change that
you have made to your .ASM file).