General :: Rearrange Header In Apache ?

I am trying to rearrange header in apache but i have run into some problems. i was able to write some with mod_header but i cannot set some headers like last modified and content length. this is what i want to do,

Firstly we have a company that can only read our xml request if the headers are in a certain order and our application doesnt send the headers in that order.

This is how the headers should look like:

And this is how it is right now:

I have used the apache to unset and set most of the but i cannot get all of them to work.