Qucik questions about plugins

[Ranma2k]

Well i'm doing my hack and it turned very well
but there is some flaw in it

Please help me by answering the following Questions

1- When the member edit his post how can i check the old post be fore he edit it ( before he compleat the edit ) what hook is responsible for this ?

2- in the hook global_start if i added a variable there will it be visable all over the fourms ?!
for example if i say

PHP Code:

 $vbulletin->userinfo['target']=  $targetuserid; 


will the variable
$vbulletin->userinfo['target'] be visable all over the forums ?


thanks