Aligning Page Numbers Right in a Header

[Variant Press]

I'm trying to create a header with text that is centered, but I want
the page number to the extreme right. Using spaces seems kind of
crude, because when the page number gets to 10 and 100, it's no longer
consistent.

For even pages (i.e. the left side page in a book) I can align the
page number left, then use the center tab for the text, but I don't
know how to align the page number right for odd-numbered pages with a
chapter title centered.

Thanks.