variable $objects_output_dir - no to specific file

[Borneq]

when I want to compile asm source, I use Settings->Compiler and debugger->Other settings->Advanced options (freat tools) and I must write: nasm -o $objects_output_dir\Asm\x86\$file_name.o $file
(my asm source is in rootSource\Asm\x86 directory
Why variable $objects_output_dir means root output .o dir, not to specific file? Is needed another variable to it like $objects_output to enable write "nasm -o $objects_output\$file_name.o $file"