Formula

I can't get the formula right, please can I ask for some help!!! 

We create our leads and need to record the company who has referred it to us.  We save these companies as accounts and with the "type of contact" from a drop down menu as "broker".   I have been trying to put together a formula on a relate field but am getting every error possible and I am at the point where I can't see the wood for the trees.  

Is this possible to do with a formula?  If there's another way to do the same thing, I'm open to suggestions :-) 

Thanks 

Rachel