[Typo3] two website within one typo

[Bart Aninowski]

I have one typo3 instalation with 2 websites (2 domains) and 2 page-tree.
I added

RewriteCond %{HTTP_HOST} mysite1.com$ [NC]
RewriteRule ^$ /index.php?id=1
RewriteRule ^[^/]*\.html$  /index.php

RewriteCond %{HTTP_HOST} mysite2.com$ [NC]
RewriteRule ^$ /index.php?id=38
RewriteRule ^[^/]*\.html$  /index.php

to my .htaccess.
Anyway I can access page from first page-tree with domain mysite2.com
fg mysite2.com/index.php?id=1
and vice versa.

How can I check if url  "mysiteX.com/index.php?id=X" belongs to correct 
page-tree and if not show "The requested page does not exist! "