Please put your related value and try this :
declare @x int, @y varchar(200),
@dt1 smalldatetime = '2014-01-21 10:00:00',
@dt2 smalldatetime = getdate()
set @x = datediff (HOUR, @dt1, @dt2)
set @y = @x * 60 - DATEDIFF(minute,@dt1, @dt2)
set @y = cast(@x as varchar(200)) + ':' + @y
Select @y