ok i got it. but it isn't user-friendly

i created a .php file named actopic.php, then i created a new cron via admincp. but now there are 2 problems left:
1. the cron is executed every month again (if i don't delete it before)
2. i still cannot change the values userid,forumid,$post[title],$post[message] and $post[poststarttime] in admincp

how can i do this? i know i need to create a new file...but problem 1 is more important.
for example:
i create a file named actopic_admin.php. with this file i can change the values and create a new cron, that executes actopic.php. at the end of actopic.php i would add a line that deletes the cron again. is this possible?
lee