Forwarding requests based on an header or RURI param

Hi guys,

I'm deploying Apache between one client and two http servers. I want Apache
to be able to decide to which http server it needs to send the client
request, based on a header or RURI param that comes on the request sent by
the client.
I'm only able to change on the RURI the parameters. The rest of the string
needs to be the same.

Can this be done with apache? and if yes, do you have a sample?

Many thanks!!