hey frnds here the full code used above
we will start with the blog module go to CP » Blog » Module settings » Fields of a new entry form: » Custom field 1 » check the 2 boxes » scroll down the page »Add "http://" prefix automatically for the fields: » check the box and save after that you need to go to CP ---> Design ---> Design management (templates) ---> Blog ---> Page with entry full text and its comments

then add this where you want the download link to appear automaticly when adding an entry:
Code
<?if ($USER_LOGGED_IN$)?><a href="$OTHER1$" target="_blank">Download this file.</a><?else?><a href="$REGISTER_LINK$" target="_blank">Available for user only.</a><?endif?>

as you see the conditional operators are already in my code so there's nothing to worry about that anymore , now just go to your blog module on your website "Add Entry" and put the download link in "Custom field 1 *:"