You will wear the proscribed uniform for your service. In the case of the Army ball that would be Army Blue Dress, the Army Service Uniform (which you will be required to have by July 2014) or the Class A Green Uniform (which will not be authorized after July 2014). Your Unit will advise you of the requirements of uniform wear for this or any special/ceremonial function.
You will not be authorized wear of the Marine Corps Blue Dress Uniform in any variation authorized by the Marine Corps for any Army function. You will be authorized wear of Decorations, Campaign Medals, Service Medals and citations as well as skill badges (with the exception of shooting iron) earned in the Marine Corps so long as it meets published DOA guidlines and regulations.
If you are going to do this best wrap your head around the fact that yoou will be a member of the United States Army....a solider and not a serving Marine. It will be difficult but you will adjust. I did.
Sgt. Rafael Peralta ,United States Marine Corps
Company A, 1st Bn, 3rd Marine Regt, 3rd Marine Divison
We will never forget your valor and sacrifice.
Semper Fi !