Yeah, I don't think I've ever seen date format characters ('y') combined with general numerals ('#' and '0'). I'm not surprised it won't work. You'll have to do this another way.

Ok, let's break this down into pieces. First, if you want ADMIN 2014-0001, then you don't want "###0" in the format string; that would get you ADMIN 2014-1 ... even if you got the other parts to work, I mean. So for that last part you're going to want '0000', not '###0'.

Second, how to combine this with the year? The value that's being formatted isn't a date, is it? I mean, if you want 2014-01-15 to be displayed as 2014-0001 and 2013-12-31 as 2013-0365, then we're talking about displaying a date in quasi-Julian format; that's one problem. But if you just have a bunch of numbers from 0 to 9999 and you want them all to appear as ADMIN 2014-nnnn then it can still be done, it's just a different problem.

One way would be to just make the custom format string "ADMIN 2014-"0000. That's great—simple and effective—but come next year you'll have change it. Is that all you need, or would you prefer something more complicated but flexible?