Workflow Soluiton

I was wondering has anyone been able to get  a way to move a user into a specific OU. At the moment am able to create a user at a top level in our AD Structure but want to move the user into a specific OU depending on what is selected.

i.e Our AD Structure is OU(Site) > OU (Users) > OU (UsersGroup)

Every Site has OU(Site) > OU (Users) however OU UsersGroup contains different OU's depending on which site.

for example BuckinghamSite has OU UserGroups> of Admin, HR, PayRoll and DowningSite has OU UserGroups> Admin, General, Booking

So at the moment I can get a new user created into OU(Site) But I'd like another Dropdown that points to OU(Users) for what ever site is selected and then show the available OU(UsersGroup) so that can move user into there?

I thought this could be obtained by my 2nd dropdown looking at the output of my get OU Site and then from that display another dropdown showing correct OUUserGroups?

Any Ideas?

At the Moment I can create user at Site level only but want to be able to move down to users>HR for example?

Would this have to be done by mappings?

Have created linked models for each individual site so that OU's are listed for each site. Am now able to create users for each site now. That's the only way I can think of resolving this issue.