Access control to poseballs?

Please bear with me as I'm all new to scripts!
I'm looking for a way to control who may use a poseball I have created. Preferable I'd be able to list specific avatars as well as avatars in a specified group. I like to keep the list in a notecard since it's going to be almost static.

I'd like to be able to add this function to the "Sit" choice, so that listed avatars may "sit", and others not in the notecard list just get a message "Not allowed" or similar.

I've browsed both here and the lslwiki, but the hits I get are far too complex for me to understand.

So, can somebody please make this function for me? I can pay for it if you want to not make it public and I'll pay you in world.

This posting belongs in the Products Wanted forum... but in case a hungry new scripter wants your L$s... they'd read the notecard at state_entry to make the whitelist of avatar names, and in the changed() handler test if llAvatarOnSitTarget() is either llSameGroup() or -1 != llListFindList(whitelist, [llKey2Name()]) ... if not, llUnSit() and llInstantMessage() them that they're not allowed. Might also llResetScript() on CHANGED_INVENTORY for when the notecard is updated.

Oh.. Sorry, and thanks a lot!