No, the 5000 will not allow any feature codes to be in a speed dial string. Sorry, but this will have to be done manually each time the destination is changed. If you are on newer software, you could configure the Configuration Assistant with an extension number and user's might find this way of changing the forwarding easier than the Remote Programming method.
Also, be wary of "double forward hopping" in the 5000 (recall to a CFA extension that goes to another extension that is CFA), as well as setting a CFA destination in DND, it can have questionable results, sometime working and other times not and sometimes resulting in unexpected behavior.