带参数的htaccess RewriteRule

i'm trying to make a rewriterule.

I want to make it like this; Surfer types

[HOST]/ttr/ttr4cmd/register/check_screenname?screenname=[PARAMETER]

Browser adress bar shows same adress,but surfer sees this page;

[HOST]/ttr/ttr4cmd/register/check_screenname.php?screenname=[PARAMETER]

So,i wrote a simple htaccess file by a generator like this;

RewriteCond %{QUERY_STRING} (^|&)screenname=($|&)
RewriteRule ^ttr/ttr4cmd/register/check_screenname$ /ttr/ttr4cmd/register/check_screenname.php?screenname=&%{QUERY_STRING}

But when i go to adress,it gives me 404 error and says

ttr/ttr4cmd/register/check_screenname is not found.

Please help me with this. Thank you :)

EDIT: I did it like this,and it worked. Thanks ^^

RewriteRule ^ttr/ttr4cmd/register/check_screenname?$ ttr/ttr4cmd/register/check_screenname.php?$1 [QSA,L]

I think you will need QSA http://httpd.apache.org/docs/2.4/rewrite/flags.html#flag_qsa

so for example

RewriteCond %{QUERY_STRING} .*screenname.*
RewriteRule ^/ttr/ttr4cmd/register/check_screenname /ttr/ttr4cmd/register/check_screenname.php [QSA]

Here you can find a good intro intro mod_rewrite http://httpd.apache.org/docs/2.4/rewrite/intro.html