IS this correct?(aligning things and getting file size)

Hi, I'm generating my own floppy disk images, because I am using a custom FS..
now what I want is to import the contents of a file(using the file directive) and then get the size of this file so that I can align it on a 512 byte sector...like if the file is 580 bytes, I want it to round up to 1024 on the next file I make..

here is my code:(it's a bit messy)

Code:

;this is just a file taking advantage of FASM and this makes a simple
;StoopidFS filesystem..this generates a complete raw bianry image..
image_start:

boot_sector:
file 'boot.bin' ;it's already aligned!

first_file:
db 0x3C ;file verification byte
dw (((first_file_end-first_file)/512)+1) ;calculate the size of the
.fname: db "kernel.bin" ;the filename string
times 16-($-.fname) db 0 ;fill in the rest of the 16bytes for the filename
dd 0x00000000 ;actual filesize(unused)
db 0x0 ;attribute byte
;;;;Actual File;;;;;

file 'kernel.bin'

first_file_end:

times ((((first_file_end-first_file)/512)+1)*512) -($-first_file) ;this should fill in the rest of the sector with 0s to align it for adding more files
;hopefully it works..










times 1474560- ($-image_start)  db 0 ;this makes sure our generated image file is exactly 1.44mb