UPDATE - U.S. Midwest business up slightly in June Monday June 30, 10:53 am ET By Ros Krasny (Adds details, background)CHICAGO, June 30 (Reuters) - Business expanded marginally in the U.S. Midwest in June, figures released on Monday showed, suggesting the manufacturing sector is still struggling to find a firm footing. The National Association of Purchasing Management-Chicago index edged up to 52.5 in June from 52.2 in May. A reading below 50 indicates a contracting regional manufacturing sector, while a reading above 50 signals expansion. Economists polled by Reuters had forecast the June index at 53.0, in a range of...