redirect old address

[kamran_dotnet]

i channge my vbulletin address from www.forum.mysite.com to www.mysite.com/forum
so my website linked by many other websites and when users click on links they astill going to old url
there is no problem but for my website SEO its bad.or maybe google think its a dublicated url

i want a change url in my .htaccess to change incoming urls from from www.forum.mysite.com to www.mysite.com/forum
what should i do?

--------------- Added [DATE]1376587053[/DATE] at [TIME]1376587053[/TIME] ---------------

also i down want to loose incoming traphics to wrong url
for example:
www.forum.mysite.com/memberlist.php
must be converted to
www.mysite.com/memberlist.php

is that possible with .htaccess 301 ?

--------------- Added [DATE]1376587557[/DATE] at [TIME]1376587557[/TIME] ---------------

i use this after search some time:

<IfModule mod_rewrite.c>
  RewriteEngine On
  RewriteCond %{HTTP_HOST} ^forum.mysite.com$ [OR]
  RewriteCond %{HTTP_HOST} ^www.mysite.com/forum/$
  RewriteRule (.*)$ http://www.mysite.com/forum/$1 [R=301,L]
</IfModule>

any idea?