need help

[idkwhattonamemyaccount]

soo im in a situation where the request data is something like this: user=XXXXX&pass=12345&check=check_login.php?username=XXXXX&password=12345

how do i make sqlmap to inject in "username=XXXXX" (the one in check_login.php)? i tried using -p username but it didnt work