HAProxy for RDP client distribution?

[Andreas Heinlein]

Hello,

I have a rather special problem to solve and would like to ask you if 
haproxy could solve it.

We need to access a windows application through RDP which does *not* 
support running under terminal services. So, on the local side, we have 
set up several identical Windows XP Pro VMs with that app. The VMs are 
running under VirtualBox on a Linux host. Each remote client uses Remote 
Desktop to access that app from their respective remote side (crude 
solution, I know, but it works).

The problem is: there are currently 12 different remote clients which 
need access, but not all at the same time. I'd like to limit the number 
of running VMs on our side to 5 and have all clients access a single 
virtual DNS name or IP address, which would then be relayed to the next 
"free" VM.

Technically speaking, we would have a pool of 5 identical "servers", 
each of which can handle only one connection at a time, and would need a 
"load balancer" which would distribute incoming connections among these 
5 servers. I think the load balancer would need to understand RDP to 
keep established connections sticky to the host it was initially 
connected to.

Can HAProxy (or any other software based solution under Linux you know 
of) solve this?

Thanks,

Andreas

P.S.: Would be nice of you could cc me on answers, as I am currently not 
subscribed to the list.