Thank you Lynne, but I already have a couple of usergroups and I don't like to do this with usergroups because I'm losing oversight then of usergroups, rights, forums etc. I'm even glad I still know what's going on at the moment.
My goal is to keep things nice and simple with usergroups and usergroup forumrights and if possible use mods to do extra things.
And if you got users already in a seperate usergroup, this option would not work, that's another reason why I'm looking for a simple mod to do this. I'm sure somebody has made a mod (maybe not here) which limits based on postcount, I would just need the periode of registration added to that.
I'm no coder but I think this musn't be too difficult to be made and it's usable for a lot of thing and maybe interested admins.
But thank you for thinking about a solution for me, really appreciate that!