I have a two page letter being sent out. The first page is on my company's letterhead, the second is not. I need a 1.6" top margin on odd pages and a 1" top margin on even pages. The side margins and the bottom margins are the same for all pages.

I am fully aware that I can set different margins page-by-page using "This point forward". I am not looking to spend that much time. I am looking for something that affects the whole document in one fell swoop.

Everything I have found posted assumes the only reason someone would need different margins is for a booklet and recommends mirrored margins. That is not what this is.

So, to summarize:
All odd pages-1.6" top margin.
All even pages-1.0" top margin.
Done in one single series of steps, not manually setting different things page by page.

Thanks for your help!