Base dropdownlist of a viewbag value

Question

Hi, i have a viewbag.Site being collected from the Active Directory, basically i am returning an id which is just a number.  I am trying to figure out how best to return a description of in a textbox on my view.

 

Viewbag.Site = 3 then 'A' else 'B' kind of thing, so far i have used a Json dropdown change function select list, however as the value has already been collected it does not trigger the dropdownlist.  I need it to be a dropdownlist so people can still change the site but it auto picks up the site they are based.

 

I would be grateful for any adivce thanks