How to get acts_as_versioned able to delete only selected ve

Hello everyone

i’m working on uploading file by using attachment_fu and
acts_as_versioned

so the problem is i can’t delete only selected version

for example ;

i have file a.txt and this file have 5 version each version is viewable
( that mean you can view version 1 , version 2 , version 3
… )

a.txt ( version1 )
a.txt ( version2)
a.txt ( version3 )
a.txt ( version 4)
a.txt (version 5 ) <<<<< latest version

and i would like to delete ONLY version 3 so the result after delete
should be like this

a.txt ( version 1)
a.txt ( version 2 )
a.txt ( version 4)
a.txt (version 5 ) <<<<< latest version

and if user choose delete version 5 , the result after delete should be
like this

a.txt (version 1)
a.txt ( version 2)
a.txt (version 4) <<<<<<<<< latest version

any suggestion ?

ps. sorry about my english